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Title:
Infrared Observations of Supernova Remnants: Spitzer and Beyond
Authors:
Temim, Tea; Woodward, C. E.; Gehrz, R. D.; Polomski, E. F.; Rudnick, L.; Roellig, T. L.
Affiliation:
AA(Univ. of Minnesota), AB(Univ. of Minnesota), AC(Univ. of Minnesota), AD(Univ. of Minnesota), AE(Univ. of Minnesota), AF(NASA Ames Research Center)
Publication:
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 210, #15.16
Publication Date:
07/2007
Origin:
AAS
Abstract Copyright:
(c) 2007: American Astronomical Society
Bibliographic Code:
2007AAS...210.1516T

Abstract

Supernova remnants (SNRs) are important laboratories for the study of a

variety of astrophysically important processes, including shock

interactions between the expanding remnant and the interstellar medium and

the condensation of dust in chemically enriched ejecta. Infrared (IR)

observations are crucial for the study of the dust content and grain

processing and for determination of grain properties and elemental

abundances in SNRs. The imaging and spectroscopic instruments on the

Spitzer Space Telescope have provided a unique opportunity to study the

composition and spatial morphology of SN ejecta and dust in SNRs. Recent

Spitzer observations of SNRs are reviewed, including observations of the

Crab and Cas A, spectroscopic monitoring of SN 1987A, and large surveys of global characteristics of SNRs in the IR. The role of IR observations in

addressing future challenges and opportunities for progress in SNR

research will also be discussed.


Title:
Jets, Rings, And Holes In Cassiopeia A: New Insights Into The Explosion
Authors:
DeLaney, Tracey; Smith, J. D.; Rudnick, L.; Rho, J.; Reach, W.; Ennis, J.; Gomez, H.; Kozasa, T.
Affiliation:
AA(MIT Kavli Institute), AB(Steward Observatory), AC(University of Minnesota), AD(Spitzer Science Center), AE(Spitzer Science Center), AF(University of Minnesota), AG(University of Wales, United Kingdom), AH(Hokkaido University, Japan)
Publication:
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 210, #15.02
Publication Date:
05/2007
Origin:
AAS
Abstract Copyright:
(c) 2007: American Astronomical Society
Bibliographic Code:
2007AAS...210.1502D

Abstract

The spectral mapping of Cassiopeia A with Spitzer has allowed us to use Doppler measurements to construct a 3-D model of the remnant structure. Combined with Doppler measurements from X-ray spectra and the locations of optical ejecta beyond the forward shock, we have gained new insights into the explosion that caused Cas A. The structure of Cas A can be characterized into "holes", "rings", and "jets". The holes refer to gaps between the front and back surfaces of the unshocked infrared ejecta that occur mostly in the plane of the sky. The shocked IR ejecta and the Si-rich X-ray ejecta form ring-like structures that line the holes in the unshocked ejecta. The well-known northeast and southwest jets extend through two of the holes in the unshocked ejecta. The Fe-rich X-ray ejecta has a different distribution from the other ejecta in that it is oriented approximately 90 degrees from the jet axis. The Fe-rich X-ray ejecta can be described as forming two jets that also extend through holes in the unshocked ejecta. The outer optical ejecta beyond the forward shock appears mostly in the plane of the sky and is certainly associated with the holes in the unshocked ejecta. Taken together, these clues indicate a series of blow-outs or jets in the plane of the sky where the highest velocity ejecta are found. The distribution of the Fe-rich ejecta provides a tidy explanation for the offset of the point source from the expansion center of the remnant and challenges the idea of overturning in the ejecta layers.

We would like to thank J. Lazendic and D. Dewey for their HETG Doppler data and M. Stage and G. Allen for their ACIS Ms Doppler data.


Title:
Extragalactic Radio Sources and the WMAP Cold Spot
Authors:
Rudnick, Lawrence; Brown, Shea; Williams, Liliya R.
Publication:
eprint arXiv:0704.0908
Publication Date:
04/2007
Origin:
ARXIV
Keywords:
Astrophysics
Comment:
submitted to ApJ Letters in shortened form
Bibliographic Code:
2007arXiv0704.0908R

Abstract

We detect a dip of 20-30% in the surface brightness and number counts of NVSS sources smoothed to a few degrees at the location of the WMAP cold spot. The dip has structure on scales of 1-10 degrees. We suggest that the dip in extragalactic brightness and number counts and the WMAP cold spot are physically related, i.e., that the coincidence is neither a statistical anomaly nor a WMAP foreground correction problem. Since the cold spot originates from structures at modest redshifts, there is no remaining need for non-Gaussian processes at the last scattering surface of the CMB. The late integrated Sachs-Wolfe effect, already seen statistically for NVSS source counts, may thus be seen to operate on a single region for the first time. To create the magnitude and angular size of the WMAP cold spot requires a completely empty void of radius 140 Mpc at z<1 along this line of sight. This is far outside the current expectations of the concordance cosmology, and adds to the anomalies seen in the CMB.

Title:
Spitzer IRAC Images and Sample Spectra of Cassiopeia A's Explosion
Authors:
Ennis, Jessica A.; Rudnick, Lawrence; Reach, William T.; Smith, J. D.; Rho, Jeonghee; DeLaney, Tracey; Gomez, Haley; Kozasa, Takashi
Affiliation:
AA(Astronomy Department, University of Minnesota, Minneapolis, MN 55455; jennis@astro.umn.edu, larry@astro.umn.edu.), AB(Astronomy Department, University of Minnesota, Minneapolis, MN 55455; jennis@astro.umn.edu, larry@astro.umn.edu.), AC(Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125; reach@ipac.caltech.edu, rho@ipac.caltech.edu.), AD(Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85712; jdsmith@as.arizona.edu.), AE(Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125; reach@ipac.caltech.edu, rho@ipac.caltech.edu.), AF(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-67, Cambridge, MA 02138; tdelaney@cfa.harvard.edu.), AG(School of Physics and Astronomy, University of Wales, P.O. Box 913, Cardiff CF24 3YB, UK; haley.gomez@astro.cf.ac.uk.), AH(Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan; kozasa@ep.sci.hokudai.ac.jp.)
Publication:
The Astrophysical Journal, Volume 652, Issue 1, pp. 376-386. (ApJ Homepage)
Publication Date:
11/2006
Origin:
UCP
ApJ Keywords:
ISM: Dust, Extinction, Infrared: ISM, ISM: Individual: Name: Cassiopeia A, Nuclear Reactions, Nucleosynthesis, Abundances, ISM: Supernova Remnants
Abstract Copyright:
(c) 2006: The American Astronomical Society
DOI:
10.1086/508142
Bibliographic Code:
2006ApJ...652..376E

Abstract

We present Spitzer IRAC images and representative 5.27-38.5 μm IRS spectra of the Cas A SNR. We find that various IRAC channels are each most sensitive to a different spectral and physical component. Channel 1 (3.6 μm) provides an excellent match to the radio synchrotron images. Where channel 1 is strong with respect to the other IRAC channels, the longer wavelength spectra show a broad continuum gently peaking around 26 μm, with weak or no lines. We suggest that this is due to unenriched progenitor circumstellar dust behind the outer shock. Where channel 4 (8 μm) is relatively brightest, the long-wavelength spectra show a strong, 2-3 μm wide peak at 21 μm, likely due to silicates and protosilicates. Strong ionic lines of [Ar II], [Ar III], [S IV], and [Ne II] also appear in these regions. We suggest that in these locations, the dust and ionic emission originate from the explosion's O-burning layers. The regions where channels 2 (4.5 μm) and 3 (5.6 μm) are strongest relative to channel 4 show a spectrum that rises gradually to 38 μm, becoming flatter longward of 21 μm, along with higher ratios of [Ne II] to [Ar II]. We suggest that the dust and ionic emission in these locations arise primarily from the C- and Ne-burning layers. All of these findings are consistent with asymmetries deep in the explosion, producing variations in the velocity structure in different directions, but generally preserving the nucleosynthetic layering. At each location, the dust and ionic lines in the mid-infrared and the hotter and more highly ionized optical and X-ray emission are then dominated by the layer currently encountering the reverse shock in that direction.

Title:
Spitzer Space Telescope Infrared Imaging and Spectroscopy of the Crab Nebula
Authors:
Temim, Tea; Gehrz, Robert D.; Woodward, Charles E.; Roellig, Thomas L.; Smith, Nathan; Rudnick, Lawrence; Polomski, Elisha F.; Davidson, Kris; Yuen, Lunming; Onaka, Takashi
Affiliation:
AA(Department of Astronomy, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; gehrz@astro.umn.edu, ttemim@astro.umn.edu, chelsea@astro.umn.edu, elwood@astro.umn.edu, larry@astro.umn.edu, kd@astro.umn.edu.), AB(Department of Astronomy, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; gehrz@astro.umn.edu, ttemim@astro.umn.edu, chelsea@astro.umn.edu, elwood@astro.umn.edu, larry@astro.umn.edu, kd@astro.umn.edu.), AC(Department of Astronomy, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; gehrz@astro.umn.edu, ttemim@astro.umn.edu, chelsea@astro.umn.edu, elwood@astro.umn.edu, larry@astro.umn.edu, kd@astro.umn.edu.), AD(NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-1000 thomas.l.roellig@nasa.gov.), AE(Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309; nathans@casa.colorado.edu.; Visiting Astronomer, Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.), AF(Department of Astronomy, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; gehrz@astro.umn.edu, ttemim@astro.umn.edu, chelsea@astro.umn.edu, elwood@astro.umn.edu, larry@astro.umn.edu, kd@astro.umn.edu.), AG(Department of Astronomy, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; gehrz@astro.umn.edu, ttemim@astro.umn.edu, chelsea@astro.umn.edu, elwood@astro.umn.edu, larry@astro.umn.edu, kd@astro.umn.edu.), AH(Department of Astronomy, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; gehrz@astro.umn.edu, ttemim@astro.umn.edu, chelsea@astro.umn.edu, elwood@astro.umn.edu, larry@astro.umn.edu, kd@astro.umn.edu.), AI(Technosciences Corporation, MS 245-6, Moffett Field, CA 94035; lyuen@mail.arc.nasa.gov.), AJ(University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; onaka@astron.s.u-tokyo.ac.jp.)
Publication:
The Astronomical Journal, Volume 132, Issue 4, pp. 1610-1623. (AJ Homepage)
Publication Date:
10/2006
Origin:
UCP
AJ Keywords:
acceleration of particles, ISM: Cosmic Rays, ISM: Individual: Name: Crab Nebula, Stars: Pulsars: Individual: Name: Crab Nebula, radiation mechanisms: nonthermal, ISM: Supernova Remnants
Abstract Copyright:
(c) 2006: The American Astronomical Society
DOI:
10.1086/507076
Bibliographic Code:
2006AJ....132.1610T

Abstract

We present 3.6, 4.5, 5.8, 8.0, 24, and 70 μm images of the Crab Nebula obtained with the Spitzer Space Telescope IRAC and MIPS cameras, low- and high-resolution Spitzer IRS spectra of selected positions within the nebula, and a near-infrared ground-based image made in the light of [Fe II] 1.644 μm. The 8.0 μm image, made with a bandpass that includes [Ar II] 7.0 μm, resembles the general morphology of visible Hα and near-IR [Fe II] line emission, while the 3.6 and 4.5 μm images are dominated by continuum synchrotron emission. The 24 and 70 μm images show enhanced emission that may be due to line emission or the presence of a small amount of warm dust in the nebula on the order of less than 1% of a solar mass. The ratio of the 3.6 and 4.5 μm images reveals a spatial variation in the synchrotron power-law index ranging from approximately 0.3 to 0.8 across the nebula. Combining this information with optical and X-ray synchrotron images, we derive a broadband spectrum that reflects the superposition of the flatter spectrum of the jet and torus with the steeper spectrum of the diffuse nebula. We also see suggestions of the expected pileup of relativistic electrons just before the exponential cutoff in the X-ray. The pulsar, and the associated equatorial toroid and polar jet structures seen in Chandra and Hubble Space Telescope images (Hester et al. 2002), can be identified in all of the IRAC images. We present the IR photometry of the pulsar. The forbidden lines identified in the high-resolution IR spectra are all double due to Doppler shifts from the front and back of the expanding nebula and give an expansion velocity of ~1264 km s-1.

Title:
X-ray Observations Of Abell 13: Understanding The X-ray And Radio Properties
Authors:
Juett, Adrienne M.; Sarazin, C. L.; Clarke, T.; Fujita, Y.; Andernach, H.; Ehle, M.; Kempner, J.; Roy, A.; Rudnick, L.
Affiliation:
AA(Univ. of Virginia), AB(Univ. of Virginia), AC(NRL), AD(Osaka University, Japan), AE(Univ. of Guanajuato, Mexico), AF(XMM-Newton SOC, Spain), AG(Bowdoin College), AH(MPIfR, Germany), AI(Univ. of Minnesota)
Publication:
American Astronomical Society, HEAD meeting #9, #15.07; Bulletin of the American Astronomical Society, Vol. 38, p.379
Publication Date:
09/2006
Origin:
AAS
Abstract Copyright:
(c) 2006: American Astronomical Society
Bibliographic Code:
2006HEAD....9.1507J

Abstract

We present results from the Chandra and XMM observations of Abell 13. This galaxy cluster contains an unusual noncentral radio source, also known as a radio relic. We present a comparison of the properties of the hot X-ray gas with those of the radio relic from VLA data, to study the interaction of the X-ray gas with the radio emitting electrons. Initial results suggest that the radio relic is associated with cooler gas in the cluster. We also present results on structure and temperature distributions of the gas in the cluster, which suggest that a recent galaxy or group merger has occurred in the cluster. From the X-ray data, we suggest that the relic was displaced from the central galaxy during the merger event.

Title:
Diffuse radio sources in groups and poor clusters
Authors:
Delain, K. M.; Rudnick, L.
Affiliation:
University of Minnesota, 116 Church St SE, Minneapolis, MN 55455, USA
Publication:
Astronomische Nachrichten, Vol.327, Issue 5/6, p.561 (AN Homepage)
Publication Date:
06/2006
Origin:
AN
Keywords:
radio continuum: general, galaxies: clusters: general, galaxies: intergalactic medium, ISM: magnetic fields
Abstract Copyright:
(c) 2006: WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI:
10.1002/asna.200610588
Bibliographic Code:
2006AN....327..561D

Abstract

We have discovered new diffuse radio sources likely associated with groups of galaxies at low redshift (0.01-0.04) and without apparent AGN by using the WENSS and WISH catalogs to perform an unbiased survey. These sources resemble the radio halos, mini-halos, and `relics' of rich clusters, which are thought to be powered by shocks and turbulence from infall into their deep potential wells. Our detection of similar sources within the shallow potential wells of groups of galaxies may challenge this model. Their radio luminosities are approximately two orders of magnitude higher than expected from the extrapolation of the apparent rich cluster radio/X-ray luminosity relation. Even if these sources are misidentified distant clusters, they would lie above the apparent rich cluster radio/X-ray luminosity relation in the literature, suggesting that detections of radio halos and relics thus far may be more biased than previously thought.

Title:
Unbiased studies of diffuse extragalactic radio sources
Authors:
Rudnick, L.; Delain, K. M.; Lemmerman, J. A.
Affiliation:
University of Minnesota, 116 Church St SE, Minneapolis, MN 55455
Publication:
Astronomische Nachrichten, Vol.327, Issue 5/6, p.549 (AN Homepage)
Publication Date:
06/2006
Origin:
AN
Keywords:
radio continuum: general, techniques: image processing, galaxies: clusters: general;intergalactic medium, cosmology: large-scale structure
Abstract Copyright:
(c) 2006: WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI:
10.1002/asna.200610585
Bibliographic Code:
2006AN....327..549R

Abstract

We present an overview of unbiased studies of diffuse extragalactic radio sources. We use a previously developed filtering technique to remove compact sources from large surveys such as WENSS, WISH, and NVSS and examine the residual diffuse emission. A search of these residuals, unbiased by optical or X-ray selection, has uncovered a wide variety of diffuse sources, including those associated with groups of galaxies, ``blank'' fields, and previously unrecognized diffuse radio galaxy emission, as well as halos and relics of rich clusters. A second, targeted survey of the brightest X-ray clusters results in a number of new sources, and illuminates some important selection effects. When the well-established relationship between X-ray and radio halo luminosities is extrapolated to lower levels, the apparent correlation holds quite well for any type of diffuse source, even background noise. The observed correlations must therefore be scrutinized for possible selection effects before physical interpretations are made. We briefly mention a wide-field mapping project to search for large-scale structures, and goals for the next generation of studies in magnetic field - angular size parameter space.

Title:
Spitzer Observations Of Tycho's Supernova Remnant: Can Dust Form In Type Ia Supernovae?
Authors:
Rho, Jeonghee; Hwang, U.; Reach, W.; Tappe, A.; DeLaney, T.; Rudnick, L.; Kozasa, T.
Affiliation:
AA(Caltech), AB(GSFC/NASA), AC(Caltech), AD(Caltech), AE(CfA), AF(UMN), AG(Hokkaido U, Japan)
Publication:
American Astronomical Society Meeting 208, #59.07; Bulletin of the American Astronomical Society, Vol. 38, p.140
Publication Date:
06/2006
Origin:
AAS
Abstract Copyright:
(c) 2006: American Astronomical Society
Bibliographic Code:
2006AAS...208.5907R

Abstract

We performed Spitzer observations of Tycho's supernova remnant--the young prototype of Ia remnants-- with the three instruments of the IRAC, IRS and MIPS. Our primary goal is to investigate formation of dust in Type Ia supernovae originated from white dwarf deflagration, which has never been observed to date. While dust formation may be inhibited in Type Ia events by the relatively higher ejecta velocities and the abundances of the radioactive material, some theoretical models suggest that dust production could occur in Type Ia events. Bright MIPS 24 and 70 micron emission is detected from the entire remnant; the global morphology is shell-like, and almost identical between the two wavelengths. While the overall infrared morphology is similar to that in the X-ray ejecta emission, the infrared emission is not clumpy like the X-rays imaged by Chandra. The infrared emission coincides the regions of the reverse shock, but the IRS spectrum shows only a featureless continuum without lines. IRAC images show faint emission, which may be consistent with the absence of ionic lines in the IRS spectrum. The IRS spectrum lacks interstellar medium spectral features and the expected mass of heated dust is indeed very small because Tycho exploded in a low-density medium and is still very young. This leads us to suggest that we may be seeing dust formation in Tycho's supernova remnant rather than shock heated dust. The spectrum can be well fit either by Glassy Carbon and/or Fe dust; C and Fe are known to have large nucleosynthetic yields from Type Ia supernovae. The estimated dust mass can be as large as 0.5 solar mass. This implies that Type Ia supernovae may be significant sites of dust formation which could help to explain the substantial quantity of dust observed in the early Universe.

Title:
Cas A Dynamics: Doppler and Proper Motion
Authors:
DeLaney, Tracey; Smith, J.; Rudnick, L.; Ennis, J.; Rho, J.; Reach, W.; Kozasa, T.; Gomez, H.
Affiliation:
AA(Harvard-Smithsonian, CfA), AB(University of Arizona), AC(University of Minnesota), AD(University of Minnesota), AE(Spitzer Science Center, Caltech), AF(Spitzer Science Center, Caltech), AG(Hokkaido University, Japan), AH(Cardiff University, United Kingdom)
Publication:
American Astronomical Society Meeting 208, #59.03; Bulletin of the American Astronomical Society, Vol. 38, p.139
Publication Date:
06/2006
Origin:
AAS
Abstract Copyright:
(c) 2006: American Astronomical Society
Bibliographic Code:
2006AAS...208.5903D

Abstract

We present Doppler velocity images of the young supernova remnant Cassiopeia A in the infrared emission lines of Ar, Ne, Si, and S observed with the Spitzer IRS and covering nearly the whole extent of the remnant. The measured infrared velocities of the shocked ejecta range from -4000 km/s to +6000 km/s. The Si and S emission near the center of the remnant, that is associated with ejecta that have not yet encountered the reverse shock, also shows both red- and blue-shifted structures with velocities between -3000 km/s and +3000 km/s. These unshocked ejecta provide a unique opportunity to study the kinematics of the explosion free from the influences of the reverse shock and CSM. The infrared kinematics are compared to optical and X-ray Doppler velocities and optical, X-ray, and radio proper motions. This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under Prime Contract between California Institute of Technology and NASA.

Title:
Nucleosynthesis Layers and Dust Formation in Cas A
Authors:
Rudnick, Lawrence; Ennis, J.; Reach, W.; Smith, J. D.; Rho, J.; DeLaney, T.; Gomez, H.; Kozasa, T.
Affiliation:
AA(University of Minnesota), AB(University of Minnesota), AC(Spitzer Science Center), AD(Steward Observatory, University of Arizona), AE(Spitzer Science Center), AF(Harvard-Smithsonian Center for Astrophysics), AG(University of Wales, United Kingdom), AH(Hokkaido University, Japan)
Publication:
American Astronomical Society Meeting 208, #59.01; Bulletin of the American Astronomical Society, Vol. 38, p.139
Publication Date:
06/2006
Origin:
AAS
Abstract Copyright:
(c) 2006: American Astronomical Society
Bibliographic Code:
2006AAS...208.5901R

Abstract

The combination of Spitzer IRAC and MIPS images and IRS 5-38 micron mapping has allowed us to isolate both the shocked circumstellar dust and the freshly formed dust in the Cassiopeia A supernova remnant. While the circumstellar dust is most clearly seen associated with the X-ray and radio and IRAC Channel 1 (synchrotron) forward shock regions, the freshly formed dust is associated with the ejecta. Ionic lines such as [Ar II] trace the distribution of the freshly formed dust, which shows a prominent spectral peak at 21 microns. Mg proto-silicates likely dominate this peak, with other silicate stretching modes visible around 9.8 microns. This dust therefore arises from deep in the O-burning layers of the explosion. We find, in isolated positions, a new type of featureless dust spectrum, whose emission appears dominated by Al2O3, and where the ionic lines of [Ar II], [Si II] and [S III] are relatively weak. This dust likely arises from higher, C-burning layers of the explosion. IRAC images from Channels 2, 3, and 4 reveal different nucleosynthetic layers, and imply asymmetries deep in the explosion which preserve these layers with little radial mixing. We conclude that the dust and ionic lines in the mid-infrared, and the hotter and more highly ionized optical and X-ray emission are then dominated by the nucleosynthesis layer currently encountering the reverse shock in each specific direction. We will briefly present evidence for other mixtures of dust components with the grain sizes and temperatures and correlation between the dust composition and the ionic lines of ejecta.This work is based, in part, on observations with the Spitzer Space Telescope, through an guest observer award issued by JPL/Caltech.

Title:
The Kinematics of the Shocked and Unshocked Ejecta in Cassiopeia A
Authors:
Delaney, T.; Smith, J. D.; Rudnick, L.; Ennis, J.; Rho, J.; Reach, W.; Kozasa, T.; Gomez, H.
Publication:
36th COSPAR Scientific Assembly. Held 16 - 23 July 2006, in Beijing, China. Meeting abstract from the CDROM, #3341
Publication Date:
00/2006
Origin:
ADS
Bibliographic Code:
2006cosp...36.3341D

Abstract

We present Doppler velocity images of the young supernova remnant Cassiopeia A in the infrared emission lines of Ar Ne Si and S observed with the Spitzer IRS and covering nearly the whole extent of the remnant The measured infrared velocities of the shocked ejecta are consistent with the optical velocities The Si and S emission near the center of the remnant that is associated with ejecta that have not yet encountered the reverse shock also shows both red- and blue-shifted structures with velocities between - 3000 km s These unshocked ejecta provide a unique opportunity to study the kinematics of the explosion free from the influences of the reverse shock and CSM

Title:
Unveiling the Nucleosynthetic Layers of Cassiopeia A with Spitzer
Authors:
Rudnick, L.; Ennis, J.; Reach, W.; Smith, J. D.; Rho, J.; DeLaney, T.; Kozasa, T.; Gomez, H.
Affiliation:
AA(Univ. of MN), AB(Univ. of MN), AC(SSC/Caltech), AD(Univ. of AZ), AE(SSC/Caltech), AF(Harvard-Smithsonian Ctr. for Astrophysics), AG(Hokkaido Univ.), AH(Cardiff Univ.)
Publication:
American Astronomical Society Meeting 207, #172.06; Bulletin of the American Astronomical Society, Vol. 37, p.1436
Publication Date:
12/2005
Origin:
AAS
Abstract Copyright:
(c) 2005: American Astronomical Society
Bibliographic Code:
2005AAS...20717206R

Abstract

We present Spitzer IRAC images of the supernova remnant Cassiopeia A, supplemented by data from the IRS, along with MIPS and near infrared images. We find that the IRAC bands each present a different view of Cas A, and highlight different layers of the explosion. IRAC Channel 1 contains a significant contribution from synchrotron radiation. It dominates over the other IRAC channels in the outer shock region. IRS spectra of bright Channel 1 regions show a broad peak around 26 microns, likely from shock heated circumstellar/interstellar dust. IRAC Channel 4 dominates the other IRAC channels where [ArII] is strong, and shows the same structures as Ar maps from IRS at 7 and 8.9 microns. These structures are similar to those seen in the optical and X-ray. IRS spectra of bright Channel 4 regions also show a sharp peak around 21 microns, likely caused by dust from the O- and Si- burning layers. Where [ArII] is weak, IRAC Channels 2 or 3 are stronger relative to Channel 4. In those regions, the IRS spectra rise gradually and then flatten longward of 23 microns, without a 21 micron peak. In the interior, we see emission from [SiII] and [SIII]. All these findings appear consistent with the idea that in each direction different nucleosynthetic layers have reached the reverse shock.

This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under Prime Contract between California Institute of Technology and NASA.


Title:
Freshly formed Dust in the Cassiopeia A supernova remnant with Spitzer
Authors:
Rho, J.; Kozasa, T.; Smith, J.; Rudnick, L.; Ennis, J.; Reach, W.; DeLaney, T.; Gomez, H.
Affiliation:
AA(Caltech), AB(Hokkaido U.), AC(UAZ), AD(UMN), AE(UMN), AF(Caltech), AG(CfA), AH(Cardiff U.)
Publication:
American Astronomical Society Meeting 207, #172.05; Bulletin of the American Astronomical Society, Vol. 37, p.1435
Publication Date:
12/2005
Origin:
AAS
Abstract Copyright:
(c) 2005: American Astronomical Society
Bibliographic Code:
2005AAS...20717205R

Abstract

Dust formation in supernovae has long been invoked to understand the large depletions of refractory elements in the ISM. Recent discovery of huge quantities of dust in galaxies and quasars at very high redshift suggests that dust was produced efficiently in the first generation of supernovae. Young supernova remnants are viable laboratories to study dust formation and the Cassiopeia A supernova remnant is the best site for it.

We performed Spitzer IRS mapping observations of Cassiopeia A. Our IRS mapping covers the entire supernova remnant of Cas A, producing mid-infrared spectra every 5 arcsec. The gas lines and continuum both were strong for most of positions, and gas lines include Ar, Ne, O, Si, S and Fe. A few dust features are identified using spectroscopy and a line-free dust map (19-23 micron) which is closely resembles the ejecta maps such as [Ar II], [O VI], and [Ne II]. A dominant dust feature is continuum which peaks at 21 micron, not seen in other astronomical objects and previously interpreted as a unique class of silicates minerals. Most of the brightest parts of the dust maps are dominated by this type of dust, and this dust is strongly correlated to [Ar II], [OIV], and [Ne II] emission, implying that dust is freshly formed in the ejecta. A second dust feature we identified is silicate emission features around 9.8 micron corresponding to the stretching mode. Most interestingly, we identified another type of dust, featureless dust, from a few positions from the dust maps, where the ejecta lines are not prominent and yet they are not from the forward shock region. Our observations confirm that the young supernova remnant Cas A is an active site of dust formation. We will discuss dust properties such as dust composition, grain sizes, temperatures of the dust, and dust formation conditions from this unique dust forming sites of the Cassiopeia A young supernova remnant.


Title:
Infrared Doppler Mapping of Cassiopeia A with Spitzer
Authors:
DeLaney, T.; Smith, J. D.; Rudnick, L.; Ennis, J.; Reach, W.; Rho, J.; Kozasa, T.; Gomez, H.
Affiliation:
AA(CfA), AB(U. of Arizona), AC(U. of Minnesota), AD(U. of Minnesota), AE(SSC), AF(SSC), AG(Hokkaido U.), AH(Cardiff U.)
Publication:
American Astronomical Society Meeting 207, #172.04; Bulletin of the American Astronomical Society, Vol. 37, p.1435
Publication Date:
12/2005
Origin:
AAS
Abstract Copyright:
(c) 2005: American Astronomical Society
Bibliographic Code:
2005AAS...20717204D

Abstract

We present Doppler velocity images of the young supernova remnant Cassiopeia A in the infrared emission lines of Ar, Ne, Si, and S observed with the Spitzer IRS and covering nearly the whole extent of the remnant. We identify many of the same structures mapped with optical spectroscopy including red- and blue-shifted rings of emission to the north and blue-shifted "parentheses" structures just southeast of the remnant center. The measured infrared velocities are consistent with the optical velocities and range between ± 6000 km/s. To the south we identify a red-shifted Ne structure that has no bright optical or X-ray counterpart. There is also bright Ne emission in the blue-shifted ring to the north, perhaps suggesting a bi-directional outflow of Ne-rich ejecta. The Si and S emission near the center of the remnant, that is possibly associated with ejecta that have not yet encountered the reverse shock, also shows both red- and blue-shifted structures with velocities between ± 2000 km/s. This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under Prime Contract between California Institute of Technology and NASA.

Title:
Canonical Particle Acceleration in FR I Radio Galaxies
Authors:
Young, Andrew; Rudnick, Lawrence; Katz, Debora; DeLaney, Tracey; Kassim, Namir E.; Makishima, Kazuo
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455.; Department of Physical Science, 425 Boehm Building, Kutztown University, Kutztown, PA 19530.), AB(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455.), AC(United States Naval Academy, 121 Blake Road, Annapolis, MD 21402.), AD(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455.; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-67, Cambridge, MA 02138.), AE(Remote Sensing Division, Naval Research Laboratory, 4555 Overlook Avenue, Washington, DC 20375-5320.), AF(Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.)
Publication:
The Astrophysical Journal, Volume 626, Issue 2, pp. 748-766. (ApJ Homepage)
Publication Date:
06/2005
Origin:
UCP
ApJ Keywords:
Acceleration of Particles, Galaxies: Active, Galaxies: Jets, Radio Continuum: Galaxies, Techniques: Image Processing
Abstract Copyright:
(c) 2005: The American Astronomical Society
DOI:
10.1086/430107
Bibliographic Code:
2005ApJ...626..748Y

Abstract

Matched-resolution multifrequency VLA observations of four radio galaxies are used to derive the asymptotic low-energy slope of the relativistic electron distribution. When available, low-energy slopes are also determined for other sources in the literature. They provide information on the acceleration physics independent of radiative and other losses, which confuse measurements of the synchrotron spectra in most radio, optical, and X-ray studies. We find a narrow range of inferred low-energy electron energy slopes n(E)~E-2.1 for the currently small sample of lower luminosity sources classified as FR I (not classical doubles). This distribution is close to, but apparently inconsistent with, the test particle limit of n(E)~E-2.0 expected from strong diffusive shock acceleration in the nonrelativistic limit. Relativistic shocks or those modified by the back-pressure of efficiently accelerated cosmic rays are two alternatives to produce somewhat steeper spectra. We note for further study the possibility of acceleration through shocks, turbulence, or shear in the flaring and brightening regions in FR I jets as they move away from the nucleus. Jets on parsec scales and the collimated jets and hot spots of FR II (classical double) sources would be governed by different acceleration sites and mechanisms; they appear to show a much wider range of spectra than those for FR I sources.

Title:
X-Ray Proper Motions in Kepler's SNR
Authors:
Robinson, P. E.; Ennis, J. A.; Rudnick, L.; DeLaney, T.; Petre, R.
Affiliation:
AA(Univ. of MN), AB(Univ. of MN), AC(Univ. of MN), AD(CfA), AE(NASA/GSFC)
Publication:
American Astronomical Society Meeting 206, #44.03; Bulletin of the American Astronomical Society, Vol. 37, p.498
Publication Date:
05/2005
Origin:
AAS
Abstract Copyright:
(c) 2000: American Astronomical Society
Bibliographic Code:
2005AAS...206.4403R

Abstract

We present the first high resolution X-ray proper motion study for Kepler's Supernova Remnant, using data from the Chandra ACIS-S3 detector in 2000 and 2004. Using a spectral analysis, we separate the X-ray emission into components dominated by the outer shock, the clumpy shocked circumstellar material, and the reverse shocked ejecta.

We show the proper motions of these various classes, which will be used to construct an overall dynamical picture of this historical SNR. We investigate the discrepancy, seen at lower resolution, of the x-ray expansion rate being twice that of the radio (Hughes 1999). This work is supported, in part, by the Harvard-Smithsonian Astrophysical Observatory under grant GO4-5075X and by the Space Telescope Science Institute under grant HST-GO-09731 to the University of Minnesota.


Title:
Spitzer Space Telescope Observations of the Crab Nebula
Authors:
Temim, T.; Woodward, C. E.; Gehrz, R. D.; Polomski, E. F.; Rudnick, L.; Davidson, K. D.
Affiliation:
AA(University of Minnesota), AB(University of Minnesota), AC(University of Minnesota), AD(University of Minnesota), AE(University of Minnesota), AF(University of Minnesota)
Publication:
American Astronomical Society Meeting 206, #44.01; Bulletin of the American Astronomical Society, Vol. 37, p.498
Publication Date:
05/2005
Origin:
AAS
Abstract Copyright:
(c) 2000: American Astronomical Society
Bibliographic Code:
2005AAS...206.4401T

Abstract

Supernova events play an important role in the study of nucleosynthesis of heavy elements and the enrichment of the interstellar medium. The Crab Nebula was formed by a supernova explosion in 1054 A.D. making it one of the youngest known supernova remnants and one of the most studied objects in the Galaxy. Here we present the first high resolution infrared images of the Crab Nebula obtained with the Spitzer Space Telescope Infrared Array Camera (IRAC) at all bands as well as the MIPS 24 micron image. The 8.0 micron image resembles the general morphology of H-α and [Fe II] line emission, while the 3.6 and 4.5 micron images seem to be dominated by continuum emission. The ratio of the 3.6 and 4.5 micron images reveals a spatial variation in the synchrotron power law index ranging from 0.2 to 0.7 across the nebula, with an overall index of 0.42. The ratio map also reveals local flux enhancements that suggest the presence of dust in the nebula. These correspond to absorption features at visible wavelengths, the cores of filaments at 8.0 microns, and the brightest features in the 24 micron image. One of these features includes the ropelike structure identified in HST WFPC2 images (see Blair et al. 1997, ApJS, 109, 473). We also find evidence for point-like emission in all bands that is coincident with the position of the puslar.

Support for this work is in part provided by NASA through contracts 1256406 and 1215746 issued by JPL/Caltech to the University of Minnesota as well as an NSF grant, Ast 02-05814.


Title:
Diffuse Radio Emission and Large Scale Structure
Authors:
Rudnick, L.; Delain, K. M.; Rawlings, S.; Brand, K.; Blundell, K.
Affiliation:
AA(University of Minnesota), AB(University of Minnesota), AC(University of Oxford), AD(University of Oxford), AE(University of Oxford)
Publication:
American Astronomical Society Meeting 206, #10.11; Bulletin of the American Astronomical Society, Vol. 37, p.445
Publication Date:
05/2005
Origin:
AAS
Abstract Copyright:
(c) 2000: American Astronomical Society
Bibliographic Code:
2005AAS...206.1011R

Abstract

We present results from a deep, low resolution VLA observation of the TONS 6o by 6o field at 90cm, and a possible detection of large scale structure in diffuse radio emission. Other studies have identified >100 Mpc superstructures in this field. We present the results of pushing into the radio confusion limit by subtracting small sources detected at higher resolution. We have removed ˜95% of the flux from the small sources using this method. We discuss the prospects of detecting large scale structure through the radio emission expected to be generated by structure formation shocks.

Partial support has been provided by NSF Grant AST-0307600 to the University of Minnesota.


Title:
Diffuse Radio Sources in Groups/Poor Clusters
Authors:
Delain, K. M.; Rudnick, L.
Affiliation:
AA(U. Minnesota), AB(U. Minnesota)
Publication:
American Astronomical Society Meeting 206, #10.10; Bulletin of the American Astronomical Society, Vol. 37, p.445
Publication Date:
05/2005
Origin:
AAS
Abstract Copyright:
(c) 2000: American Astronomical Society
Bibliographic Code:
2005AAS...206.1010D

Abstract

We present preliminary results of new diffuse radio sources without apparent AGN likely associated with groups of galaxies. We have discovered these sources through an unbiased search of the WENSS and WISH catalogs. Until now, this type of source was found exclusively in rich clusters of galaxies, probably due to selection effects. The radio halos and 'relics' of rich clusters are thought to be powered by shocks and turbulence from infall into their deep potential wells. Our detection of similar sources within the shallow potential wells of groups of galaxies challenges this model. Their radio luminosities are approximately two orders of magnitude higher than expected from the extrapolation of the apparent rich cluster radio/X-ray luminosity relation.

Partial support has been provided by NSF Grant AST-0307600 to the University of Minnesota.


Title:
X-ray, Radio, and Optical Observations of Cassiopeia A
Authors:
Delaney, T.; Rudnick, L.; Jones, T. W.; Fesen, R.; Hwang, U.; Petre, R.; Morse, J.
Affiliation:
AA(University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455, U.S.A., tdelaney@astro.umn.edu), AB(larry@astro.umn.edu), AC(twj@astro.umn.edu), AD(fesen@snr.dartmouth.edu), AE(hwang@orfeo.gsfc.nasa.gov), AF(petre@lheavx.gsfc.nasa.gov), AG(Jon.Morse@asu.edu)
Publication:
X-Ray and Radio Connections (eds. L.O. Sjouwerman and K.K Dyer) Published electronically by NRAO, http://www.aoc.nrao.edu/events/xraydio Held 3-6 February 2004 in Santa Fe, New Mexico, USA, (E4.05) 7 pages
Publication Date:
04/2005
Origin:
AUTHOR
Keywords:
X-ray, radio, supernova remnants
Abstract Copyright:
(c) with the Author(s)
Bibliographic Code:
2005xrrc.procE4.05D

Abstract

We have performed a multi-wavelength comparison of Cassiopeia A using Very Large Array, Hubble Space Telescope, and Chandra X-ray Observatory images. By separating components spectrally, we find clear associations between the emission at the three wavebands. We separate the emitting material into two components -- shocked circumstellar medium (CSM) and shocked ejecta, which show the same respective morphologies and proper motions in the different bands. In the shocked CSM, we find matched low-energy enhanced X-ray emission and optical quasi-stationary flocculi, and X-ray continuum-dominated emission matched with filamentary radio structures. In the shocked ejecta, we find matched silicon and iron dominated X-ray emission and optical fast-moving knots.

Title:
Dust and enrichment in the interstellar medium from young supernova remnants
Authors:
Tappe, Achim; Rho, Jeonghee; Reach, William T.; Rudnick, L.; Delaney, T.; Hwang, U.
Affiliation:
AA(Spitzer Science Center, Caltech/JPL, Pasadena, CA 91125, USA), AB(Spitzer Science Center, Caltech/JPL, Pasadena, CA 91125, USA), AC(Spitzer Science Center, Caltech/JPL, Pasadena, CA 91125, USA), AD(Department of Astronomy, University of Minnesota, Minneapolis, MN, USA), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA), AF(Goddard Space Flight Center, Greenbelt, MD, USA)
Publication:
Astrochemistry: Recent Successes and Current Challenges, Proceedings of the 231st Symposium of the International Astronomical Union held in Pacific Grove, California, USA, August 29-September 2, 2005. Poster sessions., p.158
Publication Date:
00/2005
Origin:
ADS
Keywords:
ISM: general, ISM: supernova remnants, stars: supernovae: individual: N132D
Comment:
IAU Symposium 231, poster session 2: poster 56
Bibliographic Code:
2005IAUS..235P.158T

Abstract

Supernovae influence the chemistry and physics in the interstellar medium from large scales down to the atomic level. However, many of the fundamental processes are still poorly understood. Supernova remnants can be used to study those processes observationally at multiple wavelengths, ranging from radio to X-rays. We have studied several young supernova remnants in our Galaxy and in the Magellanic Clouds: Tycho, Kepler, N132D, 1E102-72.3, W49B, and 3C397, using all instruments onboard the Spitzer Space Telescope, IRS, IRAC, and MIPS (Infrared Spectrograph, Infrared Array Camera, Multiband Imaging Photometer for Spitzer). Young remnants are particularly suited to study nucleosynthesis and chemical enrichment, dust formation and destruction, and the physics of shock waves. Here, we focus primarily on the oxygen-rich LMC remnant N132D (SNR 0525-69.6, cf. Figure 1). We detect bright 24, 70, and possibly 160 μm emission with MIPS. The 5-40 μm IRS spectra toward the southeastern shell show mostly a featureless, steeply rising continuum with weak [NeIII] and [OIV] lines. Our spectra also cover a fast moving ejecta knot, previously known from optical data, with much enhanced [NeIII] and [OIV] line intensities. IRAC images (3-9 μm) do not show clear evidence of emission from the remnant, partly due to confusion with the ambient ISM material, but may reveal further ejecta knots. We discuss the implications of the lack of IRAC emission and the bright infrared continuum with respect to dust formation in young SNRs, and present elemental abundance estimates from the analysis of ground state infrared lines. We complement this new Spitzer IR data with existing archival data from ISO, CHANDRA, and ground based radio studies.

Title:
HST/ACS imaging of a Balmer-dominated shock in Kepler’s supernova remnant
Authors:
Sankrit, Ravi; Blair, William P.; Delaney, Tracey; Rudnick, Lawrence; Harrus, Ilana M.; Ennis, Jessica A.
Affiliation:
AA(Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA), AB(Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA), AC(Department of Astronomy, University of Minnesota, 116 Church St., SE, Minneapolis, MN 55455, USA; Present address: Harvard-Smithsonian Center for Astrophysics, 60, Garden St., Cambridge, MA 02138 USA.), AD(Department of Astronomy, University of Minnesota, 116 Church St., SE, Minneapolis, MN 55455, USA), AE(NASA’s Goddard Space Flight Center, Building 2, Code 66.2, Greenbelt, MD 20771, USA), AF(Department of Astronomy, University of Minnesota, 116 Church St., SE, Minneapolis, MN 55455, USA)
Publication:
Advances in Space Research, Volume 35, Issue 6, p. 1027-1030. (AdSpR Homepage)
Publication Date:
00/2005
Origin:
ELSEVIER
DOI:
10.1016/j.asr.2004.11.018
Bibliographic Code:
2005AdSpR..35.1027S

Abstract

Optical images of Kepler’s supernova remnant obtained at two epochs, in 1987 at Las Campanas Observatory and in 2003 with the HST Advanced Camera for Surveys, show the motion of the Balmer-dominated forward shock. The measured proper motion, combined with estimates of the shock velocity, is used to derive a distance of 3.9-0.9+1.4 kpc to the remnant. The optical shock is clearly identified in the 0.2 0.65 keV band Chandra X-ray image of the remnant. However, there is no correlation between the optical filaments and features seen in 4 6 keV continuum dominated X-ray emission.

Title:
Observing Magnetic Fields on Large Scales
Authors:
Rudnick, Lawrence
Affiliation:
AA(Department of Astronomy, University of Minnesota, Minneapolis, MN, USA)
Publication:
Journal of the Korean Astronomical Society, vol. 37, no. 5, pp. 329-335
Publication Date:
12/2004
Origin:
JKAS
Keywords:
acceleration of particles, clusters of galaxies, cosmology: large scale structure, magnetic fields
Abstract Copyright:
(c)Korean Astronomical Society
Bibliographic Code:
2004JKAS...37..329R

Abstract

Observations of magnetic fields on scales up to several Mpc are important for understanding cluster and large-scale structure evolution. Our current census of such structures is heavily biased -- towards fields of several μG, towards fields in deep potential wells, and towards high inferred field strengths in cooling flow and other clusters from improper analysis of rotation measure data. After reviewing these biases, I show some recent results on two relics that are powered in very different ways. I describe new investigations that are now uncovering weak diffuse fields in the outskirts of clusters and other low density environments, and the good prospects for further progress.

Title:
X-Ray Tomography and Spectra of Kepler's SNR
Authors:
Ennis, J. A.; DeLaney, T.; Rudnick, L.; Sankrit, R.; Blair, W. P.; Harrus, I. M.
Affiliation:
AA(Univ. of Minnesota), AB(CfA), AC(Univ. of Minnesota), AD(JHU), AE(JHU), AF(NASA/GSFC)
Publication:
American Astronomical Society Meeting 205, #106.03; Bulletin of the American Astronomical Society, Vol. 36, p.1520
Publication Date:
12/2004
Origin:
AAS
Abstract Copyright:
(c) 2004: American Astronomical Society
Bibliographic Code:
2004AAS...20510603E

Abstract

The technique of tomography on Chandra X-ray images of Kepler's supernova remnant (SNR) is used to separate the emission from circumstellar material (CSM) and the emission from ejecta. Tomography involves taking differences between images from two different energies with a scale factor chosen to accentuate features of interest. Using images made in the low-energy (0.2 to 0.65 keV), FeL+O (0.775 to 0.85 keV), and Si (1.72 to 1.96 keV) bands, two distinct X-ray populations are identified in addition to the high energy (4 to 6 keV) component. The low-energy-enhanced component has a higher low energy:FeL+O ratio than the global spectrum and highlights central knots and a thin outer northern rim. The Si-enhanced component has a higher Si:FeL+O ratio than the global spectrum and highlights the bright northern region as well as widely scattered knots which do not coincide with the low-energy-enhanced regions. Spectra of 34 regions, including two optically-selected regions and two radio-selected regions, were extracted to isolate the difference between the two tomography-identified components, and particularly to determine whether either of these components is dominated by ejecta or CSM. The tomography images were compared to known ejecta and CSM emission from radio and optical images. Much of the X-ray CSM and ejecta emission is mixed, although determining if this a physical mixture at the contact discontinuity or a superposition along the line of sight is difficult. A relation was found between non-radiative Balmer filaments and low-energy-enhanced X-ray emission. The identification of these different components will help clarify the interaction of material in young SNRs and uncover the three-dimensional structure of Kepler's SNR. This research is supported by the Space Telescope Science Institute under grant HST-GO-09731.03.

Title:
XMM-Newton Observations of A133: A Weak Shock Passing through the Cool Core
Authors:
Fujita, Yutaka; Sarazin, Craig L.; Reiprich, Thomas H.; Andernach, H.; Ehle, M.; Murgia, M.; Rudnick, L.; Slee, O. B.
Affiliation:
AA(National Astronomical Observatory, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; yfujita@th.nao.ac.jp.; Department of Astronomical Science, Graduate University for Advanced Studies, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan.), AB(Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818 sarazin@virginia.edu, thomas@reiprich.net.), AC(Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818 sarazin@virginia.edu, thomas@reiprich.net.), AD(Departamento de Astronomía, Universidad de Guanajuato, Apartado Postal 144, Guanajuato, C. P. 36000, GTO, Mexico; heinz@astro.ugto.mx.), AE(XMM-Newton Science Operations Centre, European Space Agency, Villafranca del Castillo, P.O. Box 50727, 28080 Madrid, Spain; mehle@xmm.vilspa.esa.es.), AF(Istituto di Radioastronomia (CNR), Via Gobetti 101, I-40129 Bologna, Italy; murgia@ira.bo.cnr.it.; Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (CA), Italy.), AG(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; larry@astro.umn.edu.), AH(Australia Telescope National Facility, CSIRO, P.O. Box 76, Epping, NSW 1710, Australia; bruce.slee@atnf.csiro.au.)
Publication:
The Astrophysical Journal, Volume 616, Issue 1, pp. 157-168. (ApJ Homepage)
Publication Date:
11/2004
Origin:
UCP
ApJ Keywords:
Galaxies: Cooling Flows, Galaxies: Clusters: General, Galaxies: Clusters: Individual: Alphanumeric: A133, Galaxies: Intergalactic Medium, Radio Continuum: Galaxies, X-Rays: Galaxies: Clusters
Abstract Copyright:
(c) 2004: The American Astronomical Society
DOI:
10.1086/424807
Bibliographic Code:
2004ApJ...616..157F

Abstract

We use XMM-Newton observations of the cluster of galaxies A133 to study the X-ray spectrum of the intracluster medium (ICM). We find a cold front to the southeast of the cluster core. From the pressure profile near the cold front, we derive an upper limit to the velocity of the core relative to the rest of the cluster of less than 230 km s-1. Our previous Chandra image of A133 showed a complex, birdlike morphology in the cluster core. On the basis of the XMM-Newton spectra and hardness ratio maps, we argue that the wings of this structure are a weak shock front. The shock was probably formed outside the core of the cluster and may be heating the cluster core. Our Chandra image also showed a ``tongue'' of relatively cool gas extending from the center of the cD galaxy to the center of the radio relic. The XMM-Newton results are consistent with the idea that the tongue is the gas that has been uplifted by a buoyant radio bubble including the radio relic to the northwest of the core. Alternatively, the tongue might result from a cluster merger. The small velocity of the core suggests that the bubble including the relic has been moved by buoyancy rather than by motions of the core or the ICM. We do not find clear evidence for nonthermal X-ray emission from the radio relic. On the basis of the upper limit on the inverse Compton emission, we derive a lower limit on the magnetic field in the relic of B>=1.5 μG.

Title:
A Million Second Chandra View of Cassiopeia A
Authors:
Hwang, Una; Laming, J. Martin; Badenes, Carles; Berendse, Fred; Blondin, John; Cioffi, Denis; DeLaney, Tracey; Dewey, Daniel; Fesen, Robert; Flanagan, Kathryn A.; Fryer, Christopher L.; Ghavamian, Parviz; Hughes, John P.; Morse, Jon A.; Plucinsky, Paul P.; Petre, Robert; Pohl, Martin; Rudnick, Lawrence; Sankrit, Ravi; Slane, Patrick O.; Smith, Randall K.; Vink, Jacco; Warren, Jessica S.
Affiliation:
AA(NASA GSFC, Code 662, Greenbelt, MD 20771; hwang@milkyway.gsfc.nasa.gov, rob@milkyway.gsfc.nasa.gov, rsmith@milkyway.gsfc.nasa.gov.; University of Maryland, College Park, MD 20742.), AB(Naval Research Laboratory, Code 7674L, Washington, DC 20375; jlaming@ssd5.nrl.navy.mil.), AC(Institut d'Estudis Espacials de Catalunya, Edifici Nexus, Gran Capita 24, Desp. 2-4, E-08034 Barcelona, Spain; badenes@ieec.fcr.es.), AD(Naval Research Laboratory, Code 7655.7, Washington, DC 20375; fberendse@ssd5.nrl.navy.mil.), AE(North Carolina State University, Box 8202, Raleigh, NC 27695; john_blondin@ncsu.edu.), AF(George Washington University, Washington, DC 20052; professor@cioffi.us.), AG(University of Minnesota, 116 Church Street, Southeast, Minneapolis, MN 55455; tdelaney@astro.umn.edu, larry@astro.umn.edu.), AH(Center for Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Building 37, Cambridge, MA 02139; dd@space.mit.edu, kaf@space.mit.edu.), AI(Dartmouth College, 6127 Wilder Lab, Hanover, NH 03755; fesen@snr.dartmouth.edu.), AJ(Center for Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Building 37, Cambridge, MA 02139; dd@space.mit.edu, kaf@space.mit.edu.), AK(Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545; fryer@lanl.gov.), AL(Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218; parviz@pha.jhu.edu, ravi@pha.jhu.edu.), AM(Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854; jackph@physics.rutgers.edu, jesawyer@physics.rutgers.edu.), AN(Arizona State University, Box 871504, Tempe, AZ 85287; jon.morse@asu.edu.), AO(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; plucinsk@head.cfa.harvard.edu, slane@head.cfa.harvard.edu.), AP(NASA GSFC, Code 662, Greenbelt, MD 20771; hwang@milkyway.gsfc.nasa.gov, rob@milkyway.gsfc.nasa.gov, rsmith@milkyway.gsfc.nasa.gov.), AQ(Iowa State University, Ames, IA 50011; mkp@iastate.edu.), AR(University of Minnesota, 116 Church Street, Southeast, Minneapolis, MN 55455; tdelaney@astro.umn.edu, larry@astro.umn.edu.), AS(Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218; parviz@pha.jhu.edu, ravi@pha.jhu.edu.), AT(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; plucinsk@head.cfa.harvard.edu, slane@head.cfa.harvard.edu.), AU(NASA GSFC, Code 662, Greenbelt, MD 20771; hwang@milkyway.gsfc.nasa.gov, rob@milkyway.gsfc.nasa.gov, rsmith@milkyway.gsfc.nasa.gov.; Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218; parviz@pha.jhu.edu, ravi@pha.jhu.edu.), AV(SRON National Institute for Space Research, Sorbonnelaan 2, NL-3584 CA Utrecht, Netherlands; j.vink@sron.nl.), AW(Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854; jackph@physics.rutgers.edu, jesawyer@physics.rutgers.edu.)
Publication:
The Astrophysical Journal, Volume 615, Issue 2, pp. L117-L120. (ApJ Homepage)
Publication Date:
11/2004
Origin:
UCP
ApJ Keywords:
ISM: Supernova Remnants, Stars: Supernovae: General, X-Rays: Individual: Constellation Name: Cassiopeia A, X-Rays: ISM
Abstract Copyright:
(c) 2004: The American Astronomical Society
DOI:
10.1086/426186
Bibliographic Code:
2004ApJ...615L.117H

Abstract

We introduce a million second observation of the supernova remnant Cassiopeia A with the Chandra X-Ray Observatory. The bipolar structure of the Si-rich ejecta (northeast jet and southwest counterpart) is clearly evident in the new images, and their chemical similarity is confirmed by their spectra. These are most likely due to jets of ejecta as opposed to cavities in the circumstellar medium, since we can reject simple models for the latter. The properties of these jets and the Fe-rich ejecta will provide clues to the explosion of Cas A.

Title:
Kinematics of X-Ray-Emitting Components in Cassiopeia A
Authors:
DeLaney, Tracey; Rudnick, Lawrence; Fesen, Robert A.; Jones, T. W.; Petre, Robert; Morse, Jon A.
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; tdelaney@astro.umn.edu, larry@astro.umn.edu, twj@astro.umn.edu.), AB(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; tdelaney@astro.umn.edu, larry@astro.umn.edu, twj@astro.umn.edu.), AC(Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755; fesen@snr.dartmouth.edu.), AD(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; tdelaney@astro.umn.edu, larry@astro.umn.edu, twj@astro.umn.edu.), AE(NASA Goddard Space Flight Center, Greenbelt, MD 20771; petre@lheavx.gsfc.nasa.gov.), AF(Department of Physics and Astronomy, Arizona State University, Box 871504, Tempe, AZ 85287-1504 Jon.Morse@asu.edu.)
Publication:
The Astrophysical Journal, Volume 613, Issue 1, pp. 343-348. (ApJ Homepage)
Publication Date:
09/2004
Origin:
UCP
ApJ Keywords:
ISM: Individual: Name: Cassiopeia A, ISM: Supernova Remnants
Abstract Copyright:
(c) 2004: The American Astronomical Society
DOI:
10.1086/422906
Bibliographic Code:
2004ApJ...613..343D

Abstract

We present high-resolution X-ray proper-motion measurements of Cassiopeia A using Chandra X-Ray Observatory observations from 2000 and 2002. We separate the emission into four spectrally distinct classes: Si-dominated, Fe-dominated, low-energy-enhanced, and continuum-dominated. These classes also represent distinct spatial and kinematic components. The Si- and Fe-dominated classes are ejecta and have a mean expansion rate of 0.2% yr-1. This is the same as for the forward shock filaments but less than the 0.3% yr-1 characteristic of optical ejecta. The low-energy-enhanced spectral class possibly illuminates a clumpy circumstellar component and has a mean expansion rate of 0.05% yr-1. The continuum-dominated emission likely represents the forward shock and consists of diffuse circumstellar material, which is seen as a circular ring around the periphery of the remnant as well as projected across the center.

Title:
HST/ACS Imaging of Kepler's Supernova Remnant
Authors:
Sankrit, R.; Blair, W. P.; Rudnick, L.; Delaney, T.; Harrus, I. M.
Affiliation:
AA(JHU), AB(JHU), AC(Univ. of Minnesota), AD(Univ. of Minnesota), AE(GSFC)
Publication:
American Astronomical Society Meeting 204, #21.08; Bulletin of the American Astronomical Society, Vol. 36, p.689
Publication Date:
05/2004
Origin:
AAS
Abstract Copyright:
(c) 2004: American Astronomical Society
Bibliographic Code:
2004AAS...204.2108S

Abstract

We present observations of Kepler's supernova remnant obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope. Images obtained through narrowband filters isolating Hα , [N II] and [O III] emission show a wealth of structure on sub-arcsecond scales. There are a wide array of morphologies, and dramatic variations in the relative [N II] and [O III] brightnesses among the knots and filaments. A comparison of these HST images with ground based line filter images show that knots evolve on time scales of a decade. The proper motion of non-radiative filaments in the North indicate shock speeds of about 2000--2500 km/s.

We acknowledge support from grant HST-GO-09731.01-A to the Johns Hopkins University.


Title:
Conference Note: A Taxonomy of Extended Radio Sources in Clusters of Galaxies
Authors:
Kempner, J. C.; Blanton, E. L.; Clarke, T. E.; Enßlin, T. A.; Johnston-Hollitt, M.; Rudnick, L.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics), AB(University of Virginia), AC(University of Virginia), AD(Max-Planck-Institut für Astrophysik), AE(Leiden Observatory), AF(University of Minnesota)
Publication:
Proceedings of The Riddle of Cooling Flows in Galaxies and Clusters of Galaxies, held in Charlottesville, VA, May 31 - June 4, 2003, Eds. T. Reiprich, J. Kempner, and N. Soker. To be published electronically at http://www.astro.virginia.edu/coolflow/
Publication Date:
00/2004
Origin:
AUTHOR
Bibliographic Code:
2004rcfg.proc..335K

Abstract

At the request of the conference attendees, we have compiled a classification of extended radio sources in clusters. These range from scales of tens of parsecs to over a megaparsec in scale, and include both sources associated with AGN and sources thought to derive from the electron population in the ionized ICM. We pay special attention to distinguishing between the types of AGN in the cores of cooling flow clusters and between the multiple classes of objects referred to over the years as ``radio relics.'' We suggest new names based on physical arguments for some of these classes of objects where their commonly used names are inappropriate or confusing.

Title:
A Critical Look at Faraday Rotation Measures of Cluster Magnetic Fields
Authors:
Rudnick, L.; Blundell, K. M.
Affiliation:
AA(University of Minnesota), AB(Oxford University)
Publication:
Proceedings of The Riddle of Cooling Flows in Galaxies and Clusters of Galaxies, held in Charlottesville, VA, May 31 - June 4, 2003, Eds. T. Reiprich, J. Kempner, and N. Soker. To be published electronically at http://www.astro.virginia.edu/coolflow/
Publication Date:
00/2004
Origin:
AUTHOR
Bibliographic Code:
2004rcfg.proc..153R

Abstract

Strong magnetic fields (up to 40 μG) have been claimed for the ICM in galaxy clusters, especially those with strong cooling flows, based on studies of radio source rotation measures (RMs). The suggested evidence is of two types---studies of variations in RM across individual radio galaxies embedded in clusters, and statistical studies of background sources. We have re-examined this evidence, and find that no claims for such strong, cluster-wide fields can be supported against likely alternative explanations for the observations. We show that RM variations in embedded sources have a significant contribution from the medium local to the sources themselves, which would have to be removed before seeking evidence for cluster-pervading fields. We find that the statistical conclusions are based not on background sources, but on sources embedded in the clusters and others with unreliable RMs. When such inappropriate sources are eliminated from existing samples, only marginal evidence remains for cluster-wide fields from the RM data. Other indicators of cluster fields, such as radio halos, suggest field strength values at levels of μG or less. At such levels, the magnetic fields probably do not directly affect the dynamics of the intracluster medium, although they may still be important, e.g., for thermal conduction.

Title:
HST/ACS Imaging of Kepler's supernova remnant at age 399 years
Authors:
Sankrit, R.; Blair, W. P.; Rudnick, L.; Delaney, T.; Harrus, I. M.
Publication:
35th COSPAR Scientific Assembly. Held 18 - 25 July 2004, in Paris, France., p.2731
Publication Date:
00/2004
Origin:
ADS
Bibliographic Code:
2004cosp...35.2731S

Abstract

We present observations of Kepler's SNR (the remnant of SN1604 AD) obtained with the ACS on board the Hubble Space Telescope. Images obtained through narrowband filters isolating Hα, [N˜II] and [O˜III] emission show a wealth of structure on sub-arcsecond scales. There are a wide array of morphologies, and dramatic variations in the relative [N˜II] and [O˜III] brightnesses among the knots and filaments. A comparison of these HST images with ground based line filter images show that knots evolve on time scales of a decade. The proper motion of non-radiative filaments in the North is measurable and indicates shock speeds of about 2000--2500˜km/s. We describe the structures seen in these images and the changes in the optical emission between the two epochs of narrowband imaging, and discuss how they further our understanding of the evolution and dynamics of the remnant. We also discuss the key role of these data in on-going multiwavelength studies of Kepler's SNR, and of their importance as a fiducial for future ground and space based studies.

Title:
The first measurement of Cassiopeia A's forward shock expansion rate
Authors:
Delaney, T.; Rudnick, L.
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455, USA; tdelaney@astro.umn.edu), AB(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455, USA; tdelaney@astro.umn.edu)
Publication:
Advances in Space Research, Volume 33, Issue 4, p. 422-428. (AdSpR Homepage)
Publication Date:
00/2004
Origin:
ELSEVIER
Keywords:
Supernova remnant, Proper motion, Cassiopeia A, Forward shock, Expansion rate
Abstract Copyright:
(c) 2004 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.asr.2003.02.017
Bibliographic Code:
2004AdSpR..33..422D

Abstract

We have obtained a second epoch observation of the Cassiopeia A supernova remnant with the Chandra X-ray Observatory to measure detailed X-ray proper motions for the first time. Measurements of the X-ray continuum dominated filaments located around the edge of the remnant show expansion rates from 0.02% to 0.33% yr-1. Their median value of 0.21% yr-1 is equal to the median expansion of the bright ring as measured in X-rays. We have also re-evaluated the motion of the radio bright ring with emphasis on angle-averaged emissivity profiles. Our new measurement of the expansion of the angle-averaged radio bright ring is 0.07+/-0.03% yr-1, slower than the previous radio measurements of 0.11% yr-1 which were sensitive to the motions of small-scale features. We propose that the expansion of the small-scale bright ring features in the optical, X-ray, and radio do not represent the expansion of the reverse shock, but rather represent a brightness-weighted average of ejecta passing through and being decelerated by the reverse shock. The motion of the reverse shock is represented by the motion of the angle-averaged emissivity profile of the radio bright ring.

Title:
Untangling the Dynamics of Kepler's Supernova Remnant
Authors:
Rudnick, Lawrence
Publication:
Chandra Proposal ID #05500711
Publication Date:
09/2003
Origin:
CXC
Keywords:
Chandra Proposal ID #05500711
Bibliographic Code:
2003cxo..prop.1427R

Abstract

We propose to measure proper motions and brightness changes for compact features in Kepler's supernova remnant over a four-year baseline. The dynamical state of Kepler's supernova remnant is poorly understood. Its multiple thermal and relativistic interacting plasmas have distinct kinematics, including a factor of two velocity disparity for the cospatial X-ray and radio bright rings. The line and continuum X-ray components are spatially separated and may also have distinct kinematics. Only with a clear dynamical picture of the remnant can we study the very basic physical issues, such as the interaction of the blast wave with circumstellar wind material, and the partition of explosion energy into bulk motions, heating, and energization of the relativistic plasma.

Title:
The First Measurement of Cassiopeia A's Forward Shock Expansion Rate
Authors:
DeLaney, Tracey; Rudnick, Lawrence
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455;), AB(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455;)
Publication:
The Astrophysical Journal, Volume 589, Issue 2, pp. 818-826. (ApJ Homepage)
Publication Date:
06/2003
Origin:
UCP
ApJ Keywords:
ISM: Individual: Name: Cassiopeia A, Radio Continuum: ISM, ISM: Supernova Remnants, X-Rays: ISM
Abstract Copyright:
(c) 2003: The American Astronomical Society
DOI:
10.1086/374813
Bibliographic Code:
2003ApJ...589..818D

Abstract

We have obtained a second-epoch observation of the Cassiopeia A supernova remnant (SNR) with the Chandra X-Ray Observatory to measure detailed X-ray proper motions for the first time. Both observations are 50 ks exposures of the ACIS-S3 chip, and they are separated by 2 years. Measurements of the thin X-ray continuum-dominated filaments located around the edge of the remnant (which are identified with the forward shock) show expansion rates from 0.02% to 0.33% yr-1. Many of these filaments are therefore significantly decelerated. Their median value of 0.21% yr-1 is equal to the median expansion of the bright ring (0.21% yr-1) as measured with Einstein and ROSAT. This presents a conundrum if the motion of the bright ring is indicative of the reverse shock speed. We have also reevaluated the motion of the radio bright ring with emphasis on angle-averaged emissivity profiles. Our new measurement of the expansion of the angle-averaged radio bright ring is 0.07%+/-0.03% yr-1, somewhat slower than the previous radio measurements of 0.11% yr-1, which were sensitive to the motions of small-scale features. We propose that the expansion of the small-scale bright ring features in the optical, X-ray, and radio do not represent the expansion of the reverse shock, but rather represent a brightness-weighted average of ejecta passing through and being decelerated by the reverse shock. The motion of the reverse shock itself is then represented by the motion of the angle-averaged emissivity profile of the radio bright ring.

Title:
Lowering Inferred Cluster Magnetic Field Strengths: The Radio Galaxy Contributions
Authors:
Rudnick, Lawrence; Blundell, Katherine M.
Affiliation:
AA(University of Minnesota, Minneapolis, Minnesota.), AB(Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH, UK.)
Publication:
The Astrophysical Journal, Volume 588, Issue 1, pp. 143-154. (ApJ Homepage)
Publication Date:
05/2003
Origin:
UCP
ApJ Keywords:
Galaxies: Clusters: General, Galaxies: Individual: Alphanumeric: PKS 1246-410, Magnetic Fields, Polarization, Radio Continuum: Galaxies, X-Rays: General
Abstract Copyright:
(c) 2003: The American Astronomical Society
DOI:
10.1086/373891
Bibliographic Code:
2003ApJ...588..143R

Abstract

We present a detailed examination of the relationship between the magnetic field structures and the variations in Faraday rotation across PKS 1246-410, a radio source in the Centaurus cluster of galaxies, using data from Taylor, Fabian, & Allen. We find a significant relationship between the intrinsic position angle of the polarization and the local amount of Faraday rotation. The most plausible explanation is that most or all of the rotation is local to the source. We suggest that the rotations local to cluster radio galaxies may result either from thermal material mixed with the radio plasma, or from thin skins of warm, ionized gas in pressure balance with the observed galaxy or hot cluster atmospheres. We find that the contribution of any unrelated cluster rotation measure (RM) variations on scales of 2"-10" are less than 25 rad m-2: the standard, although model-dependent, derivation of cluster fields would then lead to an upper limit of ~0.4 μG on these scales. Inspection of the distributions of rotation measure, polarization angle, and total intensity in 3C 75, 3C 465, and Cygnus A also shows source-related Faraday effects in some locations. Many effects can mask the signatures of locally dominated RMs, so the detection of even isolated correlations can be important, although difficult to quantify statistically. In order to use radio sources such as those shown here to derive cluster-wide magnetic fields, as is commonly done, one must first remove the local contributions. This is not possible at present.

Title:
The Identification of Infrared Synchrotron Radiation from Cassiopeia A
Authors:
Jones, T. J.; Rudnick, L.; DeLaney, T.; Bowden, J.
Affiliation:
AA(Astronomy Department, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract from the National Aeronautics and Space Administration.), AB(Astronomy Department, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455), AC(Astronomy Department, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455), AD(Astronomy Department, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455)
Publication:
The Astrophysical Journal, Volume 587, Issue 1, pp. 227-234. (ApJ Homepage)
Publication Date:
04/2003
Origin:
UCP
ApJ Keywords:
Acceleration of Particles, ISM: Individual: Name: Cassiopeia A, Magnetic Fields, Polarization, Radiation Mechanisms: Nonthermal, ISM: Supernova Remnants
Abstract Copyright:
(c) 2003: The American Astronomical Society
DOI:
10.1086/368149
Bibliographic Code:
2003ApJ...587..227J

Abstract

We report the discovery of polarized flux at 2.2 μm from the bright shell of the ~320 yr old supernova remnant Cas A. The fractional polarizations are comparable at 6 cm and 2.2 μm, and the polarization angles are similar, demonstrating that synchrotron radiation from the same relativistic plasma is being observed at these widely separated wave bands. The relativistic electrons radiating at 2.2 μm have an energy of ~150 GeV, (γ~3×105), assuming an ~500 μG magnetic field. The total intensity at 2.2 μm lies close to the power-law extrapolation from radio frequencies, showing that relativistic particle acceleration is likely an ongoing process; the infrared emitting electrons were accelerated no longer than ~80 yr ago. There is a small but significant concave curvature to the spectrum, as expected if the accelerating shocks have been modified by the back pressure of the cosmic rays; given calibration uncertainties, this conclusion must be considered tentative at present. The 2.2 μm polarization angles and the emission-line filaments observed by the Hubble Space Telescope are both offset from the local radial direction by 10°-20°, providing evidence that the magnetic fields in Cas A are generated by Rayleigh-Taylor instabilities in the decelerating ejecta.

Title:
Chandra Observations of the Disruption of the Cool Core in Abell 133
Authors:
Fujita, Y.; Sarazin, C. L.; Kempner, J. C.; Rudnick, L.; Slee, O. B.; Roy, A. L.; Andernach, H.; Ehle, M.
Publication:
Matter and Energy in Clusters of Galaxies, ASP Conference Proceedings, Vol. 301. Held 23-27 April 2002 at National Central University, Chung-Li, Taiwan. Edited by Stuart Bowyer and Chorng-Yuan Hwang. San Francisco: Astronomical Society of the Pacific, 2003. ISBN: 1-58381-149-4, p.477
Publication Date:
00/2003
Origin:
ADS
Comment:
ISBN: 1-58381-149-4
Bibliographic Code:
2003ASPC..301..477F

Abstract

Not Available

Title:
High Resolution Radio Continuum Observations of the Barred Spiral Galaxy NGC 3367
Authors:
García-Barreto, J. A.; Franco, J.; Rudnick, L.
Affiliation:
AA(Instituto de Astronomía, UNAM, Apdo 70-264, México, D.F. MEXICO 04510), AB(Instituto de Astronomía, UNAM, Apdo 70-264, México, D.F. MEXICO 04510), AC(Department of Astronomy, University of Minnesota, 116 Church St., S.E. Minneapolis, MN 55455)
Publication:
Disks of Galaxies: Kinematics, Dynamics and Peturbations, ASP Conference Proceedings, Vol. 275. Edited by E. Athanassoula, A. Bosma, and R. Mujica. ISBN: 1-58381-117-6. San Francisco: Astronomical Society of the Pacific, 2002, pp.
Publication Date:
12/2002
Origin:
AUTHOR
Comment:
ISBN: 1-58381-117-6
Bibliographic Code:
2002ASPC..275..362G

Abstract

Observations with an angular resolution of 2farcs1 at 1.4 GHz and 0farcs28 at 8.4 GHz of the barred galaxy NGC 3367 are reported.

Title:
Radio Spectral Index Variations and Physical Conditions in Kepler's Supernova Remnant
Authors:
DeLaney, Tracey; Koralesky, Barron; Rudnick, Lawrence; Dickel, John R.
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; tdelaney@astro.umn.edu, barron@astro.umn.edu, larry@astro.umn.edu), AB(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; tdelaney@astro.umn.edu, barron@astro.umn.edu, larry@astro.umn.edu), AC(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; tdelaney@astro.umn.edu, barron@astro.umn.edu, larry@astro.umn.edu), AD(Astronomy Department, University of Illinois at Urbana-Champaign, Urbana, IL 61801; johnd@astro.uiuc.edu)
Publication:
The Astrophysical Journal, Volume 580, Issue 2, pp. 914-927. (ApJ Homepage)
Publication Date:
12/2002
Origin:
UCP
ApJ Keywords:
ISM: individual (Kepler's supernova remnant), Radio Continuum: ISM, ISM: Supernova Remnants
Abstract Copyright:
(c) 2002: The American Astronomical Society
DOI:
10.1086/343787
Bibliographic Code:
2002ApJ...580..914D

Abstract

A new epoch of VLA measurements of Kepler's supernova remnant (SNR) was obtained to make accurate measurements of the radio spectral index variations and polarization. We have compared these new radio images with Hα, infrared (IR), and X-ray data to better understand the three-dimensional structure and dynamics of Kepler's SNR and to better understand the physical relationships between the various nonthermal and thermal plasmas. Spatial variations in the radio spectral index from -0.85 to -0.6 are observed between 6 and 20 cm. The mean spectral index is -0.71. The mean percent polarization is 3.5% at 20 cm and 6% at 6 cm. There is a strong correspondence between the radial and azimuthal profiles of the radio, X-ray, Hα, and IR emission in different locations around the remnant, although there is no single, global pattern. Spectral tomography shows that the flat- and steep-spectrum radio emissions have distinct structures. The flat-spectrum radio emission is found at either a larger radius than or coincident with the steep-spectrum emission. We interpret these spectral components as tracing forward- and reverse-shocked material, respectively. The flat-spectrum radio emission can alternatively be interpreted as the bow shocked material (reshocked by the forward shock) from the progenitor's motion through the interstellar medium. The Hα and IR images are very similar. Their leading edges are coincident and are either in front of or coincident with the leading edges of the X-ray and radio emission. The X-ray emission matches the Hα and IR emission in places and, in other places, traces the steep-spectrum radio emission. In the north, there is also an anticorrelation in the azimuthal profiles around the remnant of the flat-spectrum radio emission and the thermal X-ray, Hα, and IR emissions. We suggest that this could be due to a relative weakening of the particle acceleration at the forward shock due to Alfvén wave damping in regions of high density.

Title:
Lower Cluster Magnetic Field Estimates - The Radio Galaxy Contribution
Authors:
Rudnick, L.; Blundell, K.
Affiliation:
AA(Univ. of Minnesota), AB(University of Oxford)
Publication:
American Astronomical Society, 201st AAS Meeting, #42.02; Bulletin of the American Astronomical Society, Vol. 34, p.1167
Publication Date:
12/2002
Origin:
AAS
Abstract Copyright:
(c) 2002: American Astronomical Society
Bibliographic Code:
2002AAS...201.4202R

Abstract

Analysis of rotation measure distributions in cluster radio galaxies shows that much of the rotation measure can originate from the individual radio source and its immediate environs. This result was obtained by comparing source polarization position angles to the observed rotation measures. Unless one can eliminate the individual source RM contributions, which is not possible at present, then only an upper limit to the strength of cluster-wide magnetic field fluctuations can be made. Using the same model-dependent assumptions as in the literature, we derive an upper limit of approximately 0.4 microGauss for fluctuating magnetic fields on scales of 0.5 - 3 kpc in the general Centaurus Cluster medium. Source-related Faraday rotation can arise either from a low density thermal medium mixed with the radio galaxy, or a higher density `skin' around the relativistic plasma. This research was supported by NSF grant AST-00-71167 at Minnesota (LR) and by a University Research Fellowship from the Royal Society (KMB).

Title:
Chandra Observations of the Disruption of the Cool Core in A133
Authors:
Fujita, Yutaka; Sarazin, Craig L.; Kempner, Joshua C.; Rudnick, L.; Slee, O. B.; Roy, A. L.; Andernach, H.; Ehle, M.
Affiliation:
AA(National Astronomical Observatory, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; yfujita@th.nao.ac.jp.; Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818 sarazin@virginia.edu, jck7k@virginia.edu.), AB(Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818 sarazin@virginia.edu, jck7k@virginia.edu.), AC(Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818 sarazin@virginia.edu, jck7k@virginia.edu.), AD(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455.), AE(Australia Telescope National Facility, CSIRO, P.O. Box 76, Epping, NSW 1710, Australia.), AF(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany.), AG(Departamento de Astronomía, Universidad de Guanajuato, A.P. 144, Guanajuato, C.P. 36000, GTO, Mexico.), AH(XMM-Newton Science Operations Centre, Apartado 50727, E-28080 Madrid, Spain.; Science Operations and Data Systems Division, Research and Scientific Support Department of ESA, ESTEC, 2200 AG Noordwijk, Netherlands.)
Publication:
The Astrophysical Journal, Volume 575, Issue 2, pp. 764-778. (ApJ Homepage)
Publication Date:
08/2002
Origin:
UCP
ApJ Keywords:
Galaxies: Cooling Flows, Galaxies: Clusters: General, Galaxies: Clusters: Individual: Alphanumeric: A133, Galaxies: Intergalactic Medium, Radio Continuum: Galaxies, X-Rays: Galaxies: Clusters
Abstract Copyright:
(c) 2002: The American Astronomical Society
DOI:
10.1086/341352
Bibliographic Code:
2002ApJ...575..764F

Abstract

We present the analysis of a Chandra observation of the galaxy cluster A133, which has a cooling flow core, a central radio source, and a diffuse, filamentary radio source that has been classified as a radio relic. The X-ray image shows that the core has a complex structure. The most prominent feature is a ``tongue'' of emission that extends from the central cD galaxy to the northwest and partly overlaps the radio relic. Spectral analysis shows that the emission from the tongue is thermal emission from relatively cool gas at a temperature of ~1.3 keV. One possibility is that this tongue is produced by Kelvin-Helmholtz (KH) instabilities through the interaction between the cold gas around the cD galaxy and hot intracluster medium. We estimate the critical velocity and timescale for the KH instability to be effective for the cold core around the cD galaxy. We find that the KH instability can disrupt the cold core if the relative velocity is >~400 km s-1. We compare the results with those of clusters in which sharp, undisrupted cold fronts have been observed; in these clusters, the low-temperature gas in their central regions has a more regular distribution. In contrast to A133, these cluster cores have longer timescales for the disruption of the core by the KH instability when they are normalized to the timescale of the cD galaxy motion. Thus, the other cores are less vulnerable to KH instability. Another possible origin of the tongue is that it is gas that has been uplifted by a buoyant bubble of nonthermal plasma that we identify with the observed radio relic. From the position of the bubble and the radio estimate of the age of the relic source, we estimate a velocity of ~700 km s-1 for the bubble. The structure of the bubble and this velocity are consistent with numerical models for such buoyant bubbles. The energy dissipated by the moving bubble may affect the cooling flow in A133. The combination of the radio and X-ray observations of the radio relic suggest that it is a relic radio lobe formerly energized by the central cD rather than a merger shock-generated cluster radio relic. The lobe may have been displaced from the central cD galaxy by the motion of the cD galaxy or by the buoyancy of the lobe.

Title:
A Multiwavelength Study of the Cassiopeia A Supernova Remnant
Authors:
Rudnick, Lawrence
Publication:
HST Proposal ID #9537
Publication Date:
07/2002
Origin:
HST
Keywords:
HST Proposal ID #9537 ISM AND CIRCUMSTELLAR
Bibliographic Code:
2002hst..prop.5883R

Abstract

We propose to use the WFPC2 archive data on supernova remnant Cas A along with new and existing Chandra and VLA data, to construct a coherent physical picture of its multiple interacting thermal and relativistic plasmas. These multiple plasmas have distinct kinematics and their relationships are poorly understood. There have been very few multiwavelength studies of any SNRs to date and none have had the high- resolution detail now available with HST and Chandra. We will first examine the behavior of shocks in an inhomogeneous environment with a comparison of clump structures in the optical, X-ray, and radio images. Our second goal is to study the amplification and ordering of magnetic fields using the Rayleigh-Taylor fingers now seen for the first time with the HST data. These will be compared with our radio polarization and our radio and X-ray proper motion measurements to test this shear amplification picture. Finally, we will use ionization state, structure, compositional differences, and dynamical information derived from the the optical and X-ray data to determine how cosmic ray acceleration, as measured by radio spectral index, is regulated in SNRs. The HST data now allow us to remedy the incomplete physical pictures derived from the individual wavebands separately, and make major steps in understanding the coupling between the multiple plasmas which control the dynamics and radiative properties of Cas A.

Title:
Electron population aging models for wide-angle tails
Authors:
Young, A.; Rudnick, L.; Katz-Stone, D. M.; O'Donoghue, A. A.
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church St. SE, 55455-0149, Minneapolis, MN, USA), AB(Department of Astronomy, University of Minnesota, 116 Church St. SE, 55455-0149, Minneapolis, MN, USA), AC(US Naval Academy, 21402-5026, Annapolis, MD, USA), AD(Department of Physics, St. Lawrence University, 13617, Canton, NY, USA)
Publication:
New Astronomy Reviews, Volume 46, Issue 2-7, p. 105-107. (NewAR Homepage)
Publication Date:
05/2002
Origin:
ELSEVIER
Abstract Copyright:
(c) 2002 Elsevier Science B.V.
Bibliographic Code:
2002NewAR..46..105Y

Abstract

Color-color diagrams have been useful in studying the spectral shapes in radio galaxies. At the workshop we presented color-color diagrams for two wide-angle tails, 1231+674 and 1433+553, and found that the standard aging models do not adequately represent the observed data. Although the JP and KP models can explain some of the observed points in the color-color diagram, they do not account for those found near the power-law line. This difficulty may be attributable to several causes. Spectral tomography has been previously used to discern two separate electron populations in these sources. The combination spectra from two such overlying components can easily resemble a range of power-laws. In addition, any non-uniformity in the magnetic field strength can also create a power-law-like spectrum. We will also discuss the effects that angular resolution has on the shape of the spectrum.

Title:
Multi-resolution imaging and spectra of extended sources
Authors:
Rudnick, Lawrence
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church St. SE, 55455-0149, Minneapolis, MN, USA)
Publication:
New Astronomy Reviews, Volume 46, Issue 2-7, p. 101-103. (NewAR Homepage)
Publication Date:
05/2002
Origin:
ELSEVIER
Abstract Copyright:
(c) 2002 Elsevier Science B.V.
Bibliographic Code:
2002NewAR..46..101R

Abstract

I introduce a straightforward technique for the filtering of extended astronomical images into components of different spatial scales. For a positive original image, each component is positive definite, and the sum of all components equals the original image. In this way, the components are each individually suitable for flux measurements and broadband spectra calculations. I present an illustration of this technique on the radio galaxy Cygnus A.

Title:
The problems of ageing
Authors:
Rudnick, Lawrence
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church St. SE, 55455-0149, Minneapolis, MN, USA)
Publication:
New Astronomy Reviews, Volume 46, Issue 2-7, p. 95-100. (NewAR Homepage)
Publication Date:
05/2002
Origin:
ELSEVIER
Abstract Copyright:
(c) 2002 Elsevier Science B.V.
Bibliographic Code:
2002NewAR..46...95R

Abstract

I present a brief overview of observational, modeling and theoretical issues related to ageing calculations based on spectral steepening. These include problems such as inhomogeneous magnetic fields, diffusion of relativistic particles, confusion from multiple particle populations and particle acceleration. Although some of the effects are only of order unity, others call into question the entire ageing paradigm. I refer to and show some data illustrating these problems and make a few recommendations about how we should proceed given these uncertainties.

Title:
The First Measurement of Cassiopeia A's Forward Shock Expansion Rate
Authors:
DeLaney, T. A.; Rudnick, L.
Affiliation:
AA(University of Minnesota), AB(University of Minnesota)
Publication:
American Astronomical Society, 200th AAS Meeting, #15.09; Bulletin of the American Astronomical Society, Vol. 34, p.666
Publication Date:
05/2002
Origin:
AAS
Abstract Copyright:
(c) 2002: American Astronomical Society
Bibliographic Code:
2002AAS...200.1509D

Abstract

We have obtained a second epoch observation of the Cassiopeia A supernova remnant with the Chandra Observatory to measure detailed X-ray proper motions for the first time. Both epoch observations are 50 ks exposures of the ACIS-S3 chip and they are separated by 2 years. Measurements of the thin continuum dominated filaments located around the edge of the remnant (that are identified with the forward shock) show expansion rates from 0.21 %/yr to 0.27 %/yr. This is only slightly faster than the expansion of the bright ring (0.20 %/yr) as measured with Einstein and ROSAT. This presents a conundrum if the motion of the bright ring is indicative of the reverse shock speed. The proper motions of knots located in the bright ring and interior of the remnant, as measured with Chandra, show a large range of speeds and directions, including inward motions. We propose that the expansion of the bright ring does not represent the expansion of the reverse shock, but rather represents a brightness weighted average of ejecta passing through the reverse shock. Alternatively, we cannot rule out whether the forward shock has recently encountered a dense shell that has slowed its expansion with no effect on the reverse shock speed. This work is supported under Smithsonian grant number SMITHSONIAN/GO1-2051A/NASA.

Title:
Simple Multiresolution Filtering and the Spectra of Radio Galaxies and Supernova Remnants
Authors:
Rudnick, L.
Affiliation:
AA(Astronomy Department, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455)
Publication:
The Publications of the Astronomical Society of the Pacific, Volume 114, Issue 794, pp. 427-449. (PASP Homepage)
Publication Date:
04/2002
Origin:
UCP
PASP Keywords:
acceleration of particles, Galaxies: Active, Methods: Data Analysis, radiation mechanisms: nonthermal, ISM: Supernova Remnants
Abstract Copyright:
(c) 2002: The Astronomical Society of the Pacific
Bibliographic Code:
2002PASP..114..427R

Abstract

A simple method is explored for examining the structures and spectral index distributions on different scales in Galactic and extragalactic radio sources, based on a multiresolution filtering technique suggested by Starck, Murtagh, & Bijaoui. Multiresolution filtering, whether in this simple algorithm or more sophisticated ones, is also useful for a wide variety of image analysis purposes. For spectral index studies, the filtering is complementary to other methods and is especially useful in separating large-scale and small-scale features with different spectral distributions. In this paper, filtered spectral distributions are produced for several sources. In the extragalactic sources, different spectral gradients are found for narrow and broad features as a function of distance from the terminal hot spots. This complicates the standard analyses used to understand relativistic particle acceleration and losses. We show that the high-field regions can yield either flatter or steeper spectra than low-field regions and be either brighter or fainter, depending on the particle history. In our supernova remnant example, Cas A, the spectra of the fine-scale features are found, in the mean, to be flatter than those on larger scales. In addition, a clear asymmetry is found in the spectral indices of the largest scale emission and is related to other physical properties of the remnant.

Title:
VLA High-Resolution 1.4 and 8.4 GHz Mapping of the Barred Galaxy NGC 3367
Authors:
García-Barreto, J. Antonio; Franco, José; Rudnick, Lawrence
Affiliation:
AA(Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, 04510, México D.F., Mexico), AB(Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, 04510, México D.F., Mexico), AC(Department of Astronomy, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455)
Publication:
The Astronomical Journal, Volume 123, Issue 4, pp. 1913-1921. (AJ Homepage)
Publication Date:
04/2002
Origin:
UCP
AJ Keywords:
Galaxies: Clusters: Individual: NGC Number: NGC 3367, Galaxies: ISM, Galaxies: Jets, Galaxies: Starburst
Abstract Copyright:
(c) 2002: The American Astronomical Society
DOI:
10.1086/339559
Bibliographic Code:
2002AJ....123.1913G

Abstract

We report new radio continuum observations with an angular resolution of 2.1" at 1.4 GHz (20 cm) and 0.28" at 8.4 GHz (3.6 cm) of the barred galaxy NGC 3367. In the map at 1.4 GHz, the central nuclear region connects to the southwest lobe, with a projected structure at a position angle (P.A.) of ~230°, forming a jetlike structure. The map at 8.4 GHz shows a compact unresolved source (smaller than 65 pc in diameter) associated with emission from the nucleus and several compact sources located within a radius of about 300 pc, forming a circumnuclear structure. The compact core, jet, and lobes form a small, low-power counterpart to radio galaxies, with a flow axis that is out of the plane of the galaxy. The flow axis (P.A.~230deg) coincides with the P.A. of the major axis of the galaxy and is thus inclined to the rotation axis of the disk. In addition, the flow axis differs by about 20° from the major axis of the stellar bar. Assuming that the stellar bar rotates counterclockwise (i.e., assuming trailing spiral arms), this difference in angle is taken as an argument in favor of having the jetlike structure out of the plane of the disk and not associated with the stellar bar.

Title:
Cas A's Multiple Plasmas - Catching the Wave
Authors:
Rudnick, L.
Affiliation:
AA(University of Minnesota)
Publication:
The High Energy Universe at Sharp Focus: Chandra Science, held in conjunction with the 113th Annual Meeting of the ASP. ASP Conference Proceedings, Vol. 262. Edited by Eric M. Schlegel and Saeqa Dil Vrtilek. ISBN: 1-58381-102-8. San Francisco: Astronomical Society of the Pacific, 2002. Publication Date: 00/2002, p.293
Publication Date:
01/2002
Origin:
ADS; AUTHOR
Comment:
ISBN: 1-58381-102-8
Bibliographic Code:
2002ASPC..262..293R

Abstract

In addition to its hot X-ray emitting gas, Cas A contains other plasmas that are important energetically, radiatively, and in terms of the diagnostics they provide for this dynamic young remnant. In this talk I will review the current state of our knowledge of these other components, with a focus on the relativistic plasma responsible for the radio emission. I will present a close look at the dynamics and spectral energy distribution, and how these help us understand relativistic particle acceleration and magnetic field amplification in the remnant. I will also discuss the expected and observed relationships between the various plasmas and how they can lead to a comprehensive picture of Cas A's evolution.

Title:
Electron distributions in cluster halos and relics
Authors:
Rudnick, Larry
Publication:
In: Highlights of Astronomy, Vol. 12, as presented at the XXIVth General Assembly of the IAU - 2000 [Manchester, UK, 7 - 18 August 2000]. Edited by H. Rickman. San Francisco, CA: Astronomical Society of the Pacific, ISBN 1-58381-086-2, 2002, p. 539 - 540
Publication Date:
00/2002
Origin:
ARI
Keywords:
Clusters of Galaxies, Halos
Abstract Copyright:
IAU
Comment:
JD10: Cluster mergers and their connection to radio sources. Eds.: L. Feretti; G. Giovannini. Abstract.; ISBN: 1-58381-086-2
Bibliographic Code:
2002HiA....12..539R

Abstract

Not Available

Title:
The discovery of 2 Micron synchrotron emission in CAS A
Authors:
Rudnick, L.; Jones, T.; Delaney, T.; Bowden, J.
Publication:
34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA., meeting abstract
Publication Date:
00/2002
Origin:
AUTHOR
Bibliographic Code:
2002cosp...34E2442R

Abstract

We report the discovery of polarized emission at 2 microns from the bright shell of the supernova remnant Cas A, at brightness levels and position angles consistent with those seen at radio wavelengths. This provides the first unambiguous evidence for synchrotron radiation from this remnant beyond the radio regime. We will discuss the implications of this result for relativistic particle acceleration, including both the epoch of acceleration in the development of the shocks and the energies to which particles are accelerated. In addition, our preliminary results show a spectrum which hardens at higher energies, as expected in some models of non-linear particle acceleration. This work has been supported, in part, by grants to the University of Minnesota from the U.S. National Science Foundation and by NASA, and was carried out on NASA's IRTF.

Title:
The First Measurement of Cassiopeia A s Forward Shock Expansion Rate
Authors:
Ddelaney, T.; Rudnick, L.
Publication:
34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA., meeting abstract
Publication Date:
00/2002
Origin:
AUTHOR
Bibliographic Code:
2002cosp...34E2438D

Abstract

We have obtained a second epoch observation of the Cassiopeia A supernova remnant with the Chandra Observatory to measure detailed X-ray proper motions for the first time. Both epoch observations are 50 ks exposures of the ACIS-S3 chip and they are separated by 2 years. Measurements of the thin continuum dominated filaments located around the edge of the remnant (that are identified with the forward shock) show expansion rates from 0.02%/yr to 0.33%/yr. The median value of 0.21%/yr is on par with the median expansion of the bright ring (0.21%/yr) as measured with Einstein and ROSAT. This presents a conundrum if the motion of the bright ring is indicative of the reverse shock speed. The proper motions of knots located in the bright ring and interior of the remnant, as measured with Chandra, show a large range of speeds and directions, including inward motions. We propose that the expansion of the bright ring does not represent the expansion of the reverse shock, but rather represents a brightness weighted average of ejecta passing through the reverse shock. Alternatively, we cannot rule out whether the forward shock has recently encountered a dense shell that has slowed its expansion with no effect on the reverse shock speed. This work is supported under Smithsonian grant number SMITHSONIAN/GO1-2051A/NASA

Title:
Spectral Shapes of Relaxed Radio Galaxy Lobes
Authors:
Young, A.; Rudnick, L.; Makishima, K.; Tashiro, M.; Iyomoto, N.; Kassim, N.; Worrall, D.
Affiliation:
AA(U. Minnesota), AB(U. Minnesota), AC(U. Tokyo), AD(U. Tokyo), AE(U. Tokyo), AF(NRL), AG(Bristol)
Publication:
American Astronomical Society, 199th AAS Meeting, #51.09; Bulletin of the American Astronomical Society, Vol. 33, p.1377
Publication Date:
12/2001
Origin:
AAS
Abstract Copyright:
(c) 2001: American Astronomical Society
Bibliographic Code:
2001AAS...199.5109Y

Abstract

We present preliminary results from VLA* observations on three radio galaxies: Fornax A, 3C386 (both FRIs) and 3C98 (FRII). All of these sources show large relaxed structures, largely devoid of hotspots and jets, and therefore likely to be statically confined by their surrounding medium. In order to compare internal pressures to those derived from any thermal extended X-ray emission, and to connect the radio emitting electrons to non-thermal X-ray emission from the Inverse Compton process, we produce spectral shapes as a function of position in these sources. Together, this information could be used in the future to calculate internal pressures by breaking the synchrotron degeneracy of particle density and magnetic field strength, and examine the mutual interactions between the relativistic and surrounding thermal plasmas. *The VLA is a facility of the National Science Foundation, operated by NRAO/AUI. This work is supported, in part, by NSF grant AST96-16964 at the University of Minnesota.

Title:
Shapes of Synchrotron Spectra from Fanaroff-Riley II sources
Authors:
Grundstrom, E.; Rudnick, L.; Blundell, K. M.
Affiliation:
AA(University of Minnesota), AB(University of Minnesota), AC(University of Oxford)
Publication:
American Astronomical Society, 199th AAS Meeting, #51.07; Bulletin of the American Astronomical Society, Vol. 33, p.1377
Publication Date:
12/2001
Origin:
AAS
Abstract Copyright:
(c) 2001: American Astronomical Society
Bibliographic Code:
2001AAS...199.5107G

Abstract

We present our spectral analysis of the Fanaroff-Riley II (FRII) sources 3C171, 3C172, and 3C356. These sources were observed with the VLA* and MERLIN between 1982 and 1992 in various combinations of 2 m, 20 cm, 6 cm, 3.6 cm and 2 cm wavelengths. Through the application of spectral tomography, we have not detected any substructure that may indicate two (or more) separate overlapping spectral electron populations. Using color-color diagrams, we fit standard synchrotron aging models to each source's spectrum. For 3C172 and 3C356, lobes and hotspots on both sides of each source are consistent with the same low energy injection index. The heavily distorted source 3C171, by contrast shows very different spectral behaviors in its two lobes. We will also discuss the implications of these findings on current ideas regarding particle acceleration in radio galaxies. Data on these sources were kindly provided by P. Alexander, R. Laing, I. Fernini and J.P. Leahy. *The VLA is a facility of the National Science Foundation, operated by NRAO/AUI. This work is supported, in part, by NSF grant AST00-71167 at the University of Minnesota.

Title:
Spectral Structure in FR II Radio Galaxies and Jets
Authors:
Treichel, Kari; Rudnick, L.; Hardcastle, M. J.; Leahy, J. P.
Affiliation:
AA(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; kari@astro.umn.edu, larry@astro.umn.edu), AB(Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455; kari@astro.umn.edu, larry@astro.umn.edu), AC(H. H. Wills Physics Laboratory, University of Bristol, Royal Fort, Tyndall Avenue, Bristol BS8 1TL, UK; M.Hardcastle@bristol.ac.uk), AD(Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire SK11 9DL, UK; jpl@jb.man.ac.uk)
Publication:
The Astrophysical Journal, Volume 561, Issue 2, pp. 691-702. (ApJ Homepage)
Publication Date:
11/2001
Origin:
UCP
ApJ Keywords:
galaxies: individual (3C 401, 3C 438), Galaxies: Jets, Galaxies: Structure, Radiation Mechanisms: Nonthermal, Radio Continuum: Galaxies
Abstract Copyright:
(c) 2001: The American Astronomical Society
DOI:
10.1086/323254
Bibliographic Code:
2001ApJ...561..691T

Abstract

Using spectral tomography to separate overlapping spectral features in a sample of FR II radio galaxies, we find a variety of spatial/spectral features that are not easily described in the context of current models. In particular, we find mixtures of flat- and steep-spectrum features in the hot spot regions and nonmonotonic spectral index gradients along jets. Additional findings include spectral gradients in compact hot spots and possible transitions in jet properties at the downstream ends of the diffuse lobes. The complexity of behaviors uncovered here points to the need for a thorough investigation of numerical models for radio galaxies, as well as for detailed observational studies of larger, unbiased samples. We also perform the first quantitative assessment of errors in the use of spectral tomography for spectral index measurements.

Title:
Chandra Detection of the Forward and Reverse Shocks in Cassiopeia A
Authors:
Gotthelf, E. V.; Koralesky, B.; Rudnick, L.; Jones, T. W.; Hwang, U.; Petre, R.
Affiliation:
AA(; Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027; evg@astro.columbia.edu.), AB(; Astronomy Department, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455.), AC(; Astronomy Department, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455.), AD(; Astronomy Department, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455.), AE(; Laboratory for High Energy Astrophysics, Goddard Space Flight Center, Baltimore, MD 20771.; Department of Astronomy, University of Maryland, College Park, MD 20742.), AF(; Laboratory for High Energy Astrophysics, Goddard Space Flight Center, Baltimore, MD 20771.)
Publication:
The Astrophysical Journal, Volume 552, Issue 1, pp. L39-L43. (ApJ Homepage)
Publication Date:
05/2001
Origin:
UCP
ApJ Keywords:
ISM: Supernova Remnants, Stars: Supernovae: Individual: Name: Cassiopeia A, X-Rays: General
Abstract Copyright:
(c) 2001: The American Astronomical Society
DOI:
10.1086/320250
Bibliographic Code:
2001ApJ...552L..39G

Abstract

We report the localization of the forward and reverse shock fronts in the young supernova remnant Cassiopeia A using X-ray data obtained with the Chandra X-Ray Observatory. High-resolution X-ray maps resolve a previously unseen X-ray feature encompassing the extremity of the remnant. This feature consists of thin, tangential wisps of emission bordering the outer edge of the thermal X-ray and radio remnant, forming a circular rim, ~2.7′ in radius. Radio images show a sharp rise in brightness at this X-ray rim along with a large jump in the synchrotron polarization angle. These characteristics suggest that these wisps are the previously unresolved signature of the forward, or outer, shock. Similarly, we identify the sharp rise in emissivity of the bright shell for both the radio and X-ray line emission associated with the reverse shock. The derived ratio of the averaged forward and reverse shock radii of ~3:2 constrains the remnant to have swept up roughly the same amount of mass as was ejected; this suggests that Cas A is just entering the Sedov phase. Comparison of the X-ray spectra from the two shock regions shows that the equivalent widths of prominent emission lines are significantly lower exterior to the bright shell, as expected if they are respectively identified with the shocked circumstellar material and shocked ejecta. Furthermore, the spectrum of the outer rim itself is dominated by power-law emission, likely the counterpart of the nonthermal component previously seen at energies above ~10 keV.

Title:
What Shape are Your Spectra In?
Authors:
Rudnick, Lawrence
Publication:
Particles and Fields in Radio Galaxies Conference, ASP Conference Proceedings Vol. 250. Edited by Robert A. Laing and Katherine M. Blundell. ISBN: 1-58381-090-0. San Francisco: Astronomical Society of the Pacific, 2001., p.372
Publication Date:
00/2001
Origin:
ADS
Comment:
ISBN: 1-58381-090-0
Bibliographic Code:
2001ASPC..250..372R

Abstract

Not Available

Title:
X-ray fluxes of radio-selected remnants
Authors:
Miller, E. A.; Rudnick, L.
Publication:
Young Supernova Remnants: Eleventh Astrophysics Conference. AIP Conference Proceedings, Vol. 565. College Park, Maryland, 16-18 Oct, 2000. Edited by Stephen S. Holt, and Una Hwang. American Institute of Physics, 2001, p.449-452 (AIPC Homepage)
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001AIPC..565..449M

Abstract

Not Available

Title:
Spectral index variations in Kepler's supernova remnant
Authors:
Delaney, Tracey; Koralesky, Barron; Rudnick, Lawrence; Dickel, John R.
Publication:
Young Supernova Remnants: Eleventh Astrophysics Conference. AIP Conference Proceedings, Vol. 565. College Park, Maryland, 16-18 Oct, 2000. Edited by Stephen S. Holt, and Una Hwang. American Institute of Physics, 2001, p.279-282 (AIPC Homepage)
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001AIPC..565..279D

Abstract

Not Available

Title:
Radio proper motions: Cas A &Kepler
Authors:
Koralesky, Barron; Rudnick, L.
Publication:
Young Supernova Remnants: Eleventh Astrophysics Conference. AIP Conference Proceedings, Vol. 565. College Park, Maryland, 16-18 Oct, 2000. Edited by Stephen S. Holt, and Una Hwang. American Institute of Physics, 2001, p.275-278 (AIPC Homepage)
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001AIPC..565..275K

Abstract

Not Available

Title:
Cas A-A Y2K status report
Authors:
Rudnick, L.
Publication:
Young Supernova Remnants: Eleventh Astrophysics Conference. AIP Conference Proceedings, Vol. 565. College Park, Maryland, 16-18 Oct, 2000. Edited by Stephen S. Holt, and Una Hwang. American Institute of Physics, 2001, p.247-256 (AIPC Homepage)
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001AIPC..565..247R

Abstract

Not Available

Title:
Spectral Behavior of Extragalactic Jets and Sheaths in Fanaroff-Riley I Sources
Authors:
Young, A.; Rudnick, L.; Katz-Stone, D. M.; Giovannini, G.
Affiliation:
AA(University of Minnesota), AB(University of Minnesota), AC(U.S. Naval Academy), AD(Istituto di Radioastronomia, CNR, Bologna)
Publication:
American Astronomical Society, 197th AAS Meeting, #75.12; Bulletin of the American Astronomical Society, Vol. 32, p.1523
Publication Date:
12/2000
Origin:
AAS
Abstract Copyright:
(c) 2000: American Astronomical Society
Bibliographic Code:
2000AAS...197.7512Y

Abstract

We examine the synchrotron spectrum of Fanaroff-Riley I (FRI) sources. In particular, we identify and analyze two spectral components of FRI sources: the jet and the sheath. We explore the question of whether these components exist as independent relativistic electron populations or originate from a single electron population. We observed 1116+28, 1243+26, and 1553+24 with the Very Large Array at 20 cm, 6 cm, and 3.6 cm. Our analysis makes use of spectral tomography and color-color diagrams (Katz-Stone et al. 1999 ApJ 516:716, 1993 ApJ 407:549). Spectral tomography is used to isolate the two spectral components while color-color diagrams are used to discern the spectral history and behavior of the jet and the sheath. From spectral tomography, we separate the jet material from the sheath material for 1116+28 and 1243+26. Early results on the spectral behavior of the jet material for 1116+28 and 1553+24 point toward a power law. Using color-color diagrams, 1116+28 as a whole shows spectral steepening away from a power law. The Jaffe-Perola model and Kardashev-Pacholczyk model can account for some, but not all, of the spectral steepening seen in 1116+28. We will present our results and discuss the implications on these aging models. This work is supported at the University of Minnesota by grant AST96-16964 from the National Science Foundation.

Title:
CAS a: First Close-Up Views of Hot Plasma Evolution
Authors:
Rudnick, Lawrence
Publication:
Chandra Proposal ID #02500308
Publication Date:
09/2000
Origin:
CXC
Keywords:
Chandra Proposal ID #02500308
Bibliographic Code:
2000cxo..prop..505R

Abstract

We propose to measure the proper motions and changes in brightness, structure and spectrum of compact features in the Cas A supernova remnant over a two-year baseline. At a fundamental level, this important remnant is governed by the physical evolution of inhomogeneities on all scales, both in its ejecta and in the circumstellar medium. Its multiple interacting plasmas - thermal and relativistic - have distinct kinematics and their relationships are poorly understood. With this very first look at the evolution of the several X-ray emitting plasmas, and our continuing extensive radio and numerical simulation programs, we will take the required next major steps in uncovering Cas A's basic physical nature. [Includes E/PO proposal.]

Title:
Electron Distributions in Cluster Halos and Relics
Authors:
Rudnick, Larry
Affiliation:
AA(University of Minnesota, Minneapolis, MN, USA)
Publication:
Cluster Mergers and their Connection to Radio Sources, 24th meeting of the IAU, Joint Discussion 10, August 2000, Manchester, England, meeting abstract.
Publication Date:
00/2000
Origin:
AUTHOR
Bibliographic Code:
2000IAUJD..10E..22R

Abstract

The advent of new X-ray observations of Inverse Compton emission from cluster relics and other sources holds great promise for establishing their physical conditions. However, the synchrotron/Compton comparisons needed for such analyses face some serious questions. First is the true spectral shape of the synchrotron electrons, which is easily distorted, e.g., by magnetic field or other gradients or inhomogeneities within the beam. Second is the decoupling between regions of high electron densities (yielding Compton emission) and high magnetic fields (yielding synchrotron emission) that is found in numerical simulations. I will illustrate the effects of these factors and suggest approaches to dealing with them.

Title:
Chandra Identification of an X-ray Bright Outer Shock Boundary Surrounding Cassiopeia-A
Authors:
Gotthelf, E. V.; Koralesky, B.; Hwang, U.; Petre, R.; Jones, T. W.; Rudnick, L.; Holt, S.
Affiliation:
AA(Columbia), AB(Minnesota), AC(NASA/GSFC), AD(NASA/GSFC), AE(Minnesota), AF(Minnesota), AG(NASA/GSFC)
Publication:
American Astronomical Society, 195th AAS Meeting, #112.06; Bulletin of the American Astronomical Society, Vol. 31, p.1540
Publication Date:
12/1999
Origin:
AAS
Abstract Copyright:
(c) 1999: American Astronomical Society
Bibliographic Code:
1999AAS...19511206G

Abstract

We have identified a sharp X-ray bright boundary at the outer edge of the young supernova remnant Cassiopeia-A using data obtained with the Chandra Observatory. Energy selected maps restricted to the high energy X-ray continuum emission-band (4-6 keV) provides direct evidence for the supernova remnant's projected outer shock front. Thin wisps (< 0.1' wide) form a circular boundary, 2.7' in radius, which is seen to encompass the bulk of the bright thermal X-ray and radio emission. This brightened edge is not evident in the X-ray line emission or the radio continuum data. VLA radio data shows large jumps in the synchrotron polarization angle along the rim, interior to which the inferred magnetic field is predominantly radial; we suggest these jumps arise from compression associated with an outer shock. We consider physical mechanisms for the observed structure. Acknowledgments: SNR research at the University of Minnesota is supported by the NASA Graduate Student Research Program and the National Science Foundation under grant AST 96-19438. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. E.V.G is supported by NASA LTSA grant NAG5-7935.

Title:
Spatial Separation of Cassiopeia A's Multiple X-ray and Radio Emitting Plasmas
Authors:
Koralesky, B.; Gotthelf, E. V.; Holt, S. S.; Hwang, U.; Jones, T. W.; Petre, R.; Rudnick, L.
Affiliation:
AA(U. Minnesota), AB(Columbia U.), AC(NASA/GSFC), AD(NASA/GSFC & University of Maryland), AE(U. Minnesota), AF(NASA/GSFC), AG(U. Minnesota)
Publication:
American Astronomical Society, 195th AAS Meeting, #112.05; Bulletin of the American Astronomical Society, Vol. 31, p.1540
Publication Date:
12/1999
Origin:
AAS
Abstract Copyright:
(c) 1999: American Astronomical Society
Bibliographic Code:
1999AAS...19511205K

Abstract

Through comparisons among Chandra silicon line and high energy continuum images and VLA radio observations we see clear signatures for multiple plasmas in the Cassiopeia A supernova remnant. On large scales (>15") we find that the radio and X-ray emissions are linearly correlated, but with different slopes interior and exterior to the bright ring, as opposed to previous analyses. We discuss the implications for differing particle acceleration and magnetic field amplification processes behind the apparent outer and reverse shocks. The small scale (<5") X-ray brightness is uncorrelated with the local radio brightness. Ignoring the actual brightness, we find no global correlation between X-ray and radio features, only a partial overlap. This provides a limit to the contribution from synchrotron emission at several keV and argues that magnetic field amplification regions can be separated from the shocked thermal plasma on scales of 0.1 pc. In addition, only half of the silicon line and high energy emission overlap on small scales, which further demonstrates that multiple components are present. Spectral information on these components are discussed on an accompanying poster. SNR research at the University of Minnesota is supported by the NASA Graduate Student Research Program and the National Science Foundation under grant AST 96-19438. E.V.G. is supported by NASA LTSA grant NAG5-7935. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Title:
The Supernova Remnant Cassiopeia A at Millimeter Wavelengths
Authors:
Wright, Melvyn; Dickel, John; Koralesky, Barron; Rudnick, Lawrence
Publication:
The Astrophysical Journal, Volume 518, Issue 1, pp. 284-297. (ApJ Homepage)
Publication Date:
06/1999
Origin:
APJ
ApJ Keywords:
ISM: INDIVIDUAL (CASSIOPEIA A), ISM: STRUCTURE, RADIATION MECHANISMS: NONTHERMAL, RADIO CONTINUUM: GENERAL, ISM: SUPERNOVA REMNANTS
Abstract Copyright:
(c) 1999: The American Astronomical Society
DOI:
10.1086/307270
Bibliographic Code:
1999ApJ...518..284W

Abstract

We used the BIMA array to map the supernova remnant Cas A from 28 to 87 GHz with 2" to 7" angular resolution. Data from 75 to 87 GHz with 19 pointing centers were combined with single-dish data to form a completely sampled image. These new BIMA images were compared with VLA images at 1.5 and 5 GHz to look for spectral index variations across Cas A. The images were spatially filtered and convolved to a common sampled UV range corresponding to angular scales from 7" to 95". The images give direct evidence for a steeper spectral index in the knots outside the bright ring. Analysis of the 26 brightest peaks gives statistical evidence for spectral index variations throughout the remnant. The high-frequency spectra confirm and extend the spectral variations seen previously at lower frequencies. The spectra are largely consistent with different power laws and not curved spectra. This provides strong support for local variations in the acceleration of relativistic particles in Cas A.

Title:
Coaxial Jets and Sheaths in Wide-Angle-tailed Radio Galaxies
Authors:
Katz-Stone, D. M.; Rudnick, L.; Butenhoff, C.; O'Donoghue, A. A.
Publication:
The Astrophysical Journal, Volume 516, Issue 2, pp. 716-728. (ApJ Homepage)
Publication Date:
05/1999
Origin:
APJ
ApJ Keywords:
GALAXIES: INDIVIDUAL (1231+674, 1433+553), GALAXIES: JETS, GALAXIES: KINEMATICS AND DYNAMICS, GALAXIES: STRUCTURE, POLARIZATION
Abstract Copyright:
(c) 1999: The American Astronomical Society
DOI:
10.1086/307123
Bibliographic Code:
1999ApJ...516..716K

Abstract

We add 20, 6, and 3.6 cm VLA observations of two wide-angle tails (WATs), 1231+674 and 1433+553, to existing VLA data at 6 and 20 cm in order to study the variations of spectral index as a function of position. We apply the spectral tomography process that we introduced in our analysis of 3C 67, 3C 190, and 3C 449 (Katz-Stone Katz-Stone & Rudnick). Both spectral tomography and polarization maps indicate that there are two distinct extended components in each source. As in the case of 3C 449, we find that each source has a flat spectrum jet surrounded by a steeper spectrum sheath. The steep components tend to be more highly polarized than the flat components. We discuss a number of possibilities for the dynamics of the jet/sheath systems and the evolution of their relativistic electron populations. Although the exact nature of these two coaxial components is still uncertain, their existence requires new models of jets in FR I sources and may also have implications for the dichotomy between FR I and FR II galaxies.

Title:
The Supernova Remnant Cas A at Millimeter Wavelengths
Authors:
Wright, M.; Dickel, J.; Koralesky, B.; Rudnick, L.
Publication:
NCSA Astronomy Digital Image Library
Publication Date:
02/1999
Origin:
NCSA
Bibliographic Code:
1997ADIL...JD...01D

Abstract

We used the BIMA array to map the supernova remnant Cas A from 28 to 87 GHz with 2" to 7" angular resolution. Data from 75 to 87 GHz, with 19 pointing centers were combined with single dish data to form a completely sampled image. These new BIMA images were compared with VLA images at 1.5 and 5 GHz to look for spectral index variations across Cas A. The images were spatially filtered and convolved to a common sampled uv-range corresponding to angular scales from 7" to 95". The images give direct evidence for a steeper spectral index in the knots outside the bright ring. Analysis of the 26 brightest peaks gives statistical evidence for spectral index variations throughout the remnant. The high frequency spectra confirm and extend the spectral variations seen previously at lower frequencies. The spectra are largely consistent with different power laws, and not curved spectra. This provides strong support for local variations in the acceleration of relativistic particles in Cas A.

Title:
Electron Populations of Wide Angle Tailed Radio Sources
Authors:
Young, A.; Rudnick, L.; Katz-Stone, D.; Butenhoff, C.; O'Donoghue, A. A.
Affiliation:
AA(U. Minnesota), AB(U. Minnesota), AC(US Naval Academy), AD(U. Calgary), AE(St. Lawrence U.)
Publication:
American Astronomical Society, 193rd AAS Meeting, #05.10; Bulletin of the American Astronomical Society, Vol. 30, p.1251
Publication Date:
12/1998
Origin:
AAS
Abstract Copyright:
(c) 1998: American Astronomical Society
Bibliographic Code:
1998AAS...193.0510Y

Abstract

In previous studies, we have shown that Wide Angle Tail radio galaxies (WATs) are comprised of narrow, flat spectrum jets, surrounded by more diffuse, steep spectrum sheaths. Here, we present our analysis of VLA observations at L, C, and X bands on WATs 1231+674 and 1433+553. We use both spectral tomography and a new multiresolution filtering technique to explore the spectral index variations between the jet and diffuse emission. Without the confusion of mixed spectral indices, we can obtain a color-color diagram of the WATs and examine their spectral shapes in the context of standard models. While none of the standard models alone could explain the spectrum seen in our similar analysis of Cygnus A, magnetic field irregularities may have significantly affected its spectrum. We will present our new results on the spectral shapes of the jets and diffuse emission and compare our findings with theoretical expectations for the evolution of the electron populations. This work is supported at the University of Minnesota by AST 96-16964 from the National Science Foundation.

Title:
The X-Ray Expansion of the Supernova Remnant Cassiopeia A
Authors:
Koralesky, Barron; Rudnick, L.; Gotthelf, E. V.; Keohane, J. W.
Publication:
Astrophysical Journal Letters v.505, p.L27 (ApJ Homepage)
Publication Date:
09/1998
Origin:
APJ
ApJ Keywords:
ISM: SUPERNOVA REMNANTS, ISM: INDIVIDUAL NAME: CASSIOPEIA A, ISM: KINEMATICS AND DYNAMICS
Abstract Copyright:
(c) 1998: The American Astronomical Society
DOI:
10.1086/311604
Bibliographic Code:
1998ApJ...505L..27K

Abstract

We present the first X-ray expansion measurements of the young, bright supernova remnant Cas A. We have acquired a deep (232 ks) ROSAT high-resolution image of Cas A that is compared with archival images of similar quality taken 17 yr earlier with the Einstein Observatory. The average expansion rate between the two epochs is found to be 0.20%+/-0.01% yr-1, twice as fast as the expansion of the bright radio ring and two-thirds as fast as the ensemble of optical fast-moving knots. This argues that we are observing a fundamentally different hydrodynamical structure in each band, although all of these components are located on the same patchy ring. In addition, we detect significant variations in the expansion rate as a function of azimuth around the bright X-ray ring. These results are discussed in the context of two classes of models, one involving a preexisting circumstellar shell and the other having a uniform or gradiated density profile that decreases monotonically away from the center.

Title:
Central Activity in the Barred Galaxy NGC 3367
Authors:
García-Barreto, J. A.; Rudnick, L.; Franco, J.; Martos, M.
Affiliation:
AA(Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, 04510 México, D.F., Mexico), AB(Department of Astronomy, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455), AC(Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, 04510 México D.F., Mexico), AD(Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, 04510 México D.F., Mexico)
Publication:
The Astronomical Journal, Volume 116, Issue 1, pp. 111-118. (AJ Homepage)
Publication Date:
07/1998
Origin:
AJ
AJ Keywords:
GALAXIES: CLUSTERS: INDIVIDUAL (NGC 3367), GALAXIES: STRUCTURE, GALAXIES: INTERGALACTIC MEDIUM, GALAXIES: QUASARS: EMISSION LINES
Abstract Copyright:
The American Astronomical Society
DOI:
10.1086/300436
Bibliographic Code:
1998AJ....116..111G

Abstract

We report the radio continuum structure of the barred galaxy NGC 3367 with an angular resolution of ~4.5". The radio structure indicates emission from the disk and from a triple source consisting of the nucleus straddled by two extended sources (the lobes). The triple source shows an excess of radio continuum emission compared with the emission expected from the total radio-Hα correlation, suggesting a nonthermal origin probably related to activity of an active galactic nucleus (AGN) and not to star formation processes. The triple source is approximately 12 kpc in extent at P.A. ~ 40 deg, close to (but not aligned with) that of the stellar bar, P.A. ~ 65 deg. Only the southwest lobe is polarized. The polarization asymmetry between the two lobes suggests that the triple-source axis is slightly out of the plane. If the origin of the emission is an outflow of plasma from an AGN, as seen in weak radio galaxies and NGC 1068, then NGC 3367 provides an excellent laboratory object to study a possible interaction of the ejected material and the barred galaxy.

Title:
Identifying Shock Structures in Supernova Remnants
Authors:
Koralesky, Barron; Rudnick, L.; Goss, W. M.; Frail, D. A.; Claussen, M. J.; Petre, R.; Gotthelf, E. V.; Keohane, J. W.; Wright, M. C. H.; Dickel, John R.; Green, A. J.
Affiliation:
AA(U of MN), AB(U of MN), AC(NRAO/AOC), AD(NRAO/AOC), AE(NRAO/AOC), AF(NASA/GSFC), AG(NASA/GSFC), AH(NASA/GSFC), AI(U of C, Berkeley), AJ(U of IL, U-C), AK(U. of Sydney)
Publication:
American Astronomical Society, 192nd AAS Meeting, #53.06; Bulletin of the American Astronomical Society, Vol. 30, p.893
Publication Date:
05/1998
Origin:
AAS
Abstract Copyright:
(c) 1998: American Astronomical Society
Bibliographic Code:
1998AAS...192.5306K

Abstract

Using observations and theory, we have attempted to identify and quantify shock structures in young and intermediate aged SNRs. This poster outlines several studies currently underway to study these shocks. By comparing measurements to simulations we have developed a method to classify a remnant's dynamical age according to the classical stages of free expansion through the Sedov-Taylor phase. We have found both Cas A and Kepler's SNRs to be in the intermediary phase between free expansion and Sedov-Taylor. We have utilized OH(1720) masers as a tool to find shock positions and to prove SNR-molecular cloud interactions. These masers have also allowed us to measure milliGauss magnetic fields in the shocks of two remnants. We have found spectral index variations in Cas A over a large range of frequency, which is consistent with many power-law distributions of electron energies. Preliminary expansion measurements of Cas A in the x-ray will also be presented, which will help define shock structures in this remnant. SNR research at the University of Minnesota is supported by the NASA Graduate Research Program and the National Science Foundation under grant AST 96-19438.

Title:
Spectral Variation in Radio Galaxies
Authors:
Treichel, K.; Rudnick, L.
Affiliation:
AA(U. of Minnesota), AB(U. of Minnesota)
Publication:
American Astronomical Society, 192nd AAS Meeting, #11.14; Bulletin of the American Astronomical Society, Vol. 30, p.833
Publication Date:
05/1998
Origin:
AAS
Abstract Copyright:
(c) 1998: American Astronomical Society
Bibliographic Code:
1998AAS...192.1114T

Abstract

We have investigated a small set of radio galaxies whose maps have been taken from the literature. Using spectral tomography techniques, we have analyzed the variations in spectral index of these galaxies. We will present some preliminary findings. These include evidence of jets that show no significant spectral variations along their lengths, weak structures that run parallel to some jets, and a mixture of flat and steep spectrum structures in the hot spots of these galaxies. We will also briefly discuss the implications of these findings for the energization and transport of relativistic particles in radio galaxies. This work is supported at the University of Minnesota by grant AST96-16964 from the National Science Foundation.

Title:
10^51 Ergs: The Evolution of Shell Supernova Remnants
Authors:
Jones, T. W.; Rudnick, Lawrence; Jun, Byung-Il; Borkowski, Kazimierz J.; Dubner, Gloria; Frail, Dale A.; Kang, Hyesung; Kassim, Namir E.; McCray, Richard
Affiliation:
AA(Department of Astronomy, University of Minnesota, Minneapolis, MN 55455), AB(Department of Astronomy, University of Minnesota, Minneapolis, MN 55455), AC(Department of Astronomy, University of Minnesota, Minneapolis, MN 55455), AD(Department of Physics, North Carolina State University, Raleigh, NC 27695-8202), AE(Instituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina), AF(National Radio Astronomy Observatory, Socorro, NM 87801), AG(Department of Astronomy, University of Washington, Seattle, WA 98195-1580), AH(Naval Research Laboratory, Washington, DC 20375-5351), AI(JILA, University of Colorado, Boulder, CO 80309-0440)
Publication:
The Publications of the Astronomical Society of the Pacific, Volume 110, Issue 744, pp. 125-151. (PASP Homepage)
Publication Date:
02/1998
Origin:
PASP
PASP Keywords:
ISM: COSMIC RAYS, INTERSTELLAR MEDIUM, PULSARS, ISM: SUPERNOVA REMNANTS
PASP/ApJ Keywords:
SUPERNOVA REMNANTS, ISM: KINEMATICS AND DYNAMICS, ISM: ABUNDANCES
Abstract Copyright:
Astronomical Society of the Pacific
Bibliographic Code:
1998PASP..110..125J

Abstract

This paper reports on the workshop ``10^51 Ergs: The Evolution of Shell Supernova Remnants,'' hosted by the University of Minnesota, 1997 March 23-26. The workshop was designed to address fundamental dynamical issues associated with the evolution of shell supernova remnants and to understand better the relationships between supernova remnants and their environments. Although the title points only to classical, shell SNR structures, the workshop also considered dynamical issues involving X-ray-filled composite remnants and pulsar-driven shells, such as that in the Crab Nebula. Approximately 75 observers, theorists, and numerical simulators with wide-ranging interests attended the workshop. An even larger community helped through extensive on-line debates prior to the meeting to focus issues and galvanize discussion. In order to deflect thinking away from traditional patterns, the workshop was organized around chronological sessions for ``very young,'' ``young,'' ``mature,'' and ``old'' remnants, with the implicit recognition that these labels are often difficult to apply. Special sessions were devoted to related issues in plerions and ``thermal X-ray composites.'' Controversy and debate were encouraged. Each session also addressed some underlying, general physical themes: How are supernova remnant (SNR) dynamics and structures modified by the character of the circumstellar medium (CSM) and the interstellar medium (ISM), and vice versa? How are magnetic fields generated in SNRs and how do magnetic fields influence SNRs? Where and how are cosmic rays (electrons and ions) produced in SNRs, and how does their presence influence or reveal SNR dynamics? How does SNR blast energy partition into various components over time, and what controls conversion between components? In lieu of a proceedings volume, we present here a synopsis of the workshop in the form of brief summaries of the workshop sessions. The sharpest impressions from the workshop were the crucial and underappreciated roles that environments have on SNR appearance and dynamics and the critical need for broad-based studies to understand these beautiful but enigmatic objects.

Title:
A Spectral Analysis of 3C 67 and 3C 190
Authors:
Katz-Stone, D. M.; Rudnick, L.
Affiliation:
AA(US Naval Academy, Annapolis, MD 21402-5026, U.S.A.), AB(University of Minnesota, Minneapolis, MN 55455, U.S.A.)
Publication:
Radio Emission from Galactic and Extragalactic Compact Sources, ASP Conference Series, Volume 144, IAU Colloquium 164, eds. J.A. Zensus, G.B. Taylor, & J.M. Wrobel, p. 181.
Publication Date:
00/1998
Origin:
AUTHOR
Bibliographic Code:
1998ASPC..144..181K

Abstract

Using new high resolution VLA and VLBA data and existing MERLIN data of 3C 67 and 3C 190, we find both sources have a complex spectral structure similar to larger Fanaroff-Riley type II sources. Our analysis of 3C 190 predicts either an unusually steep injection index of -0.8 and a young age, or a superposition of different age spectral components.

Title:
An Analysis of the Synchrotron Spectrum in the Fanaroff-Riley Type I Galaxy 3C 449
Authors:
Katz-Stone, D. M.; Rudnick, L.
Publication:
Astrophysical Journal v.488, p.146 (ApJ Homepage)
Publication Date:
10/1997
Origin:
APJ
ApJ Keywords:
GALAXIES: INDIVIDUAL ALPHANUMERIC: 3C 449, GALAXIES: JETS, GALAXIES: STRUCTURE, RADIO CONTINUUM: GALAXIES, RADIATION MECHANISMS: NONTHERMAL
Abstract Copyright:
(c) 1997: The American Astronomical Society
DOI:
10.1086/304661
Bibliographic Code:
1997ApJ...488..146K

Abstract

We studied the evolution of relativistic electrons in the Fanaroff-Riley type I (FR I) galaxy 3C 449, by observing with the VLA at three frequencies (330, 1445, and 4835 MHz) and in all four configurations for a primary resolution of 3."6. The conventional model for this type of source is that the relativistic electrons are accelerated in the core and subsequently lose energy as the jet flows outward, expands, and bends downstream. We find that 3C 449 is more complicated than that, with evidence for a different type of structure, more reminiscent of higher luminosity FR II galaxies. We introduce a new analysis tool---the spectral tomography gallery---and find evidence for two spectral components that we label the "flat jet" and the "sheath." The flat jet remains fairly well collimated throughout the inner 5', with the sheath accounting for most of the observed widening. The flat jet shows little steepening with distance from the core. However, the sheath has a steeper spectral index than the jet. If the same spectral shape is appropriate for both components, there may be an evolutionary connection between the particles in the flat jet and those in the sheath. Another possibility is that the sheath has a steeper injection index than the flat jet. This may mean that the sheath and flat jet are separate electron populations. In either case, the standard aging analyses would give incorrect answers because of confusion between the separate spectral components.

Title:
A Spectral Analysis of Two Compact Steep-Spectrum Sources
Authors:
Katz-Stone, D. M.; Rudnick, L.
Publication:
Astrophysical Journal v.479, p.258 (ApJ Homepage)
Publication Date:
04/1997
Origin:
APJ
ApJ Keywords:
GALAXIES: EVOLUTION, GALAXIES: INDIVIDUAL ALPHANUMERIC: 3C 190, GALAXIES: INDIVIDUAL ALPHANUMERIC: 3C 67, GALAXIES: STELLAR CONTENT, RADIO CONTINUUM: GALAXIES
Abstract Copyright:
(c) 1997: The American Astronomical Society
DOI:
10.1086/303882
Bibliographic Code:
1997ApJ...479..258K

Abstract

We have added new high-resolution VLA and VLBA data of two compact steep-spectrum sources (CSSs) (3C 67 and 3C 190) to existing data. We find both sources have a complex spectral structure that is not completely resolved with these data. A standard aging analysis of 3C 190 predicts an unusually steep injection index of -0.8 and a young age. If CSSs are found to have steep injection indices in general, then it suggests that they are not simply younger, smaller versions of large radio sources, but a different type of object. Another possibility is that the injection index is -0.5 and that the superposition of aged spectral components makes the injection index appear steeper. Whichever explanation is appropriate, interpretation of spectral data in such conventional terms as aging must be made cautiously.

Title:
A Comparison of X-Ray and Radio Emission from the Supernova Remnant Cassiopeia A
Authors:
Keohane, Jonathan W.; Rudnick, Lawrence; Anderson, Martha C.
Publication:
Astrophysical Journal v.466, p.309 (ApJ Homepage)
Publication Date:
07/1996
Origin:
APJ
ApJ Keywords:
ISM: INDIVIDUAL NAME: CASSIOPEIA A, ISM: STRUCTURE, RADIO CONTINUUM: ISM, ISM: SUPERNOVA REMNANTS, X-RAYS: ISM
DOI:
10.1086/177511
Bibliographic Code:
1996ApJ...466..309K

Abstract



Title:
Azimuthal Asymmetries in the Expansion of SNR Cassiopeia A
Authors:
Koralesky, B.; Rudnick, L.
Affiliation:
AA(Univ. of MN), AB(Univ. of MN)
Publication:
American Astronomical Society, 188th AAS Meeting, #74.06; Bulletin of the American Astronomical Society, Vol. 28, p.948
Publication Date:
05/1996
Origin:
AAS
Abstract Copyright:
(c) 1996: American Astronomical Society
Bibliographic Code:
1996AAS...188.7406K

Abstract

Using VLA maps of Cas A at 6cm over a time baseline of 11 years we have found azimuthal asymmetries in the expansion of the diffuse radio ring of this shell-type SNR. The range of these azimuthal variation is a factor of two in expansion rate, which in turn implies dynamical ages from 750 years to 1,500 years. The lowest expansion rate corresponds to the region where Cas A is interacting with a molecular cloud. The variations in dynamical age suggest that at different azimuthal angles, Cas A is in different evolutionary stages. We will compare the observed brightness changes of the diffuse ring with those expected from adiabatic expansion losses. We will also compare these results to other work on the motions of compact radio and optical features.

Title:
CAS A - The Movie
Authors:
Rudnick, L.; Koralesky, B.; Butenhoff, C.; Anderson, M. C.; Keohane, J.; Perley, R.
Affiliation:
AA(U. Minn.), AB(U. Minn.), AC(U. Minn.), AD(U. Wisc.), AE(U. Minn & NASA-GSFC), AF(NRAO)
Publication:
American Astronomical Society, 188th AAS Meeting, #74.03; Bulletin of the American Astronomical Society, Vol. 28, p.947
Publication Date:
05/1996
Origin:
AAS
Abstract Copyright:
(c) 1996: American Astronomical Society
Bibliographic Code:
1996AAS...188.7403R

Abstract

We present a movie of the evolving radio emission from 1978 to 1994 of the supernova remnant Cassiopeia A. The images are at a resolution of 1.3 arcseconds and an observing wavelength of 6cm, taken at the Cambridge 5km and Very Large Array radio interferometers. In the movie, one can see the overall expansion of the remnant by approximately 1.3 percent, high velocity knots and bow shocks, large filamentary and cellular structures, dark lanes moving across extended emission, and a variety of features evolving in brightness and structure. The velocity structure in the remnant is complex, and the movie allows one to disentangle overlapping features moving at different speeds and directions. Some structures, on both large and small scales, are seen moving backwards, towards the center of the remnant. We will briefly discuss possible physical interpretations of the observed features. This work is supported, in part, by NSF grant AST93-18959 at the University of Minnesota.

Title:
The Evolution of the Relativistic Particles and the Structure of the Magnetic Field in Extragalactic Radio Sources
Authors:
Katz-Stone, D. M.; Rudnick, L.
Affiliation:
AA(US Naval Academy), AB(U. Minnesota)
Publication:
American Astronomical Society, 188th AAS Meeting, #16.05; Bulletin of the American Astronomical Society, Vol. 28, p.847
Publication Date:
05/1996
Origin:
AAS
Abstract Copyright:
(c) 1996: American Astronomical Society
Bibliographic Code:
1996AAS...188.1605K

Abstract

This thesis focuses on understanding the physical mechanisms, the structures and the dynamics of extragalactic radio sources. Our methods center upon extracting the information contained in the observed synchrotron spectrum. This work includes both original radio observations as well as an analysis of existing data. Through a re-examination of the data taken by Carilli et al. (1991) of Cygnus A, we find, contrary to previous analysis, that a single curved spectrum can explain the spectral variations in the entire radio source. We then use the shape of the curved spectrum to disentangle the synchrotron parameters; we identify rings and a channel in the eastern lobe of Cygnus A which are most likely density enhanced features. We observed the Fanaroff and Riley (1974) type I (FR I) source 3C449 at three frequencies with the VLA in an effort to determine the shape of the synchrotron spectrum just after the particles are initially accelerated. We find that the injection spectrum is a power law and that there is little variation in the spectrum of the jet for 50 kpc. However, our results show that the jet is embedded in a steeper spectrum sheath. We supplemented pre-existing data of two Wide Angle Tail (WAT) sources with new observations taken with the VLA. We find that these WATs, like 3C449, have flat spectrum jets surrounded by steep spectrum sheaths. The two component structure of 3C449 and the WATs has not only been led to mistakes in previous spectral analyses, but also impacts the general models of FR I sources which were thought to have simple structures and dynamics. We added our VLA and VLBA observations of two Compact Steep Spectrum sources (CSSs) to pre-existing MERLIN observations. We find that both of these sources (3C67 and 3C190) have complex spectral structures. In addition, 3C190 appears to have a steep injection index which leads to a 50 kyr age, much younger than larger sources. As with all the sources studied in this thesis, however, a careful analysis recognizing the contributions and confusion due to multiple spectral components, needs to be carried out.

Title:
Sites of Relativistic Particle Acceleration in Supernova Remnant Cassiopeia A
Authors:
Anderson, M. C.; Rudnick, L.
Publication:
Astrophysical Journal v.456, p.234 (ApJ Homepage)
Publication Date:
01/1996
Origin:
APJ
ApJ Keywords:
ACCELERATION OF PARTICLES, ISM: COSMIC RAYS, ISM: INDIVIDUAL NAME: CASSIOPEIA A, RADIATION MECHANISMS: NONTHERMAL, RADIO CONTINUUM: ISM, ISM: SUPERNOVA REMNANTS
DOI:
10.1086/176644
Bibliographic Code:
1996ApJ...456..234A

Abstract



Title:
The Spectral and Spatial Decomposition of Extragalactic Radio Sources
Authors:
Rudnick, L.; Katz-Stone, D. M.
Publication:
Extragalactic radio sources: proceedings of the 175th Symposium of the International Astronomical Union, held in Bologna, Italy, 10-14 October 1995. Edited by Ron D. Ekers, C. Fanti, and L. Padrielli. Published by Kluwer Academic Publishers, p. 489.
Publication Date:
00/1996
Origin:
ADS
Bibliographic Code:
1996IAUS..175..489R

Abstract

Not Available

Title:
Powerful diagnostics of Cygnus A's relativistic electrons
Authors:
Rudnick, Lawrence; Katz-Stone, Debora
Publication:
Cygnus A -- Studay of a Radio Galaxy, Proceedings of the Greenbank Workshop, held in Greenbank, West Virginia, 1-4 May, 1995. Edited by C.L. Carilli and D.E. Harris. ISBN 0521553431, Cambridge University Press, 1996., p.158
Publication Date:
00/1996
Origin:
ADS
Comment:
ISBN: 0521553431
Bibliographic Code:
1996cyga.book..158R

Abstract

Not Available

Title:
Uncovering Buried Jet Treasures
Authors:
Rudnick, L.; Katz-Stone, Debora M.
Publication:
Energy transport in radio galaxies and quasars Astronomical Society of the Pacific Conference Series, Volume 100, Proceedings of a workshop held in Tuscaloosa, Alabama, 19-23 September 1995, SanFrancisco: Astronomical Society of the Pacific (ASP), |c1996, edited by Hardee, Philip E.; Bridle, Alan H.; Zensus, J. Anton, p.233
Publication Date:
00/1996
Origin:
ADS
Bibliographic Code:
1996ASPC..100..233R

Abstract

Introduction; New Analysis Tools; Sheaths and Jets; Ageless Electrons; Conclusions

Title:
Spectral and Polarization Tomography
Authors:
Katz-Stone, Debora; Rudnick, L.
Affiliation:
AA(US Naval Academy), AB(U. of MN)
Publication:
American Astronomical Society, 187th AAS Meeting, #100.01; Bulletin of the American Astronomical Society, Vol. 27, p.1425
Publication Date:
12/1995
Origin:
AAS
Abstract Copyright:
(c) 1995: American Astronomical Society
Bibliographic Code:
1995AAS...18710001K

Abstract

We present simple but powerful new analysis techniques for pairs of astronomical images. These techniques are useful for isolating features that have been blended because they are along the same line of sight. In order to be separable, the features must have different spectral or polarization properties. In spectral tomography, we construct a gallery of images by varying the factor t in the equation: B_t(x,y) \equiv B_1(x,y) - t \times B_2(x,y) where B_1 and B_2 are images at two different bands. Features with a specific color, e.g., B-V = 2.5 x log(t), or spectral index alpha = log(t) x log((nu1 )/(nu2 )) will disappear from their respective tomography images. In polarization tomography, we create a gallery of single Stokes parameter images from the original Q and U images: Q_t(x,y) \equiv Q(x,y) \times cos(t) + U(x,y) \times sin(t) In such projections, even confusion from destructive interference between components can disappear. These techniques have been applied to VLA images of radio galaxies and supernova remnants, and will probably be useful in other applications as well. We will show examples of important new dynamical and spectral features in radio sources that have been uncovered with these techniques. This work is supported in part at the University of Minnesota through NSF grant AST93-18959.

Title:
Relativistic Electron Populations in Cassiopeia A
Authors:
Anderson, M.; Rudnick, L.; Leppik, P.; Perley, R.; Braun, R.
Publication:
NCSA Astronomy Digital Image Library
Publication Date:
06/1995
Origin:
NCSA
Keywords:
BRIGHTNESS DISTRIBUTION, CASSIOPEIA A, ELECTRON ACCELERATION, PARTICLE ACCELERATION, RADIANT FLUX DENSITY, RADIO EMISSION, RELATIVISTIC PARTICLES, SPECTRAL ENERGY DISTRIBUTION, STELLAR RADIATION, SUPERNOVA REMNANTS, VERY LARGE ARRAY (VLA)
Bibliographic Code:
1995ADIL...MA...01A

Abstract

The radio structure of the galactic supernova remnant Cas A is complex and is distributed over a variety of spatial scales. A few major components are apparent. The most prominent is a bright ring of radio emission at a radius of approximately 110" (1.7 pc at a distance of 2.9 pc). This bright ring is generally associated with a region of high magnetic field, amplified through Rayleigh-Taylor instabilities which develop at the contact surface between the comparatively dense supernova ejecta and the shock-heated interstellar medium as the remnant begins to decelerate. The bright ring has an expansion age of 950 yr, much longer than that of the fast-moving optical knots situated at a similar radius (300 yr), indicating that a substantial deceleration of the radio-emitting ejecta has already occurred. A plateau, or outer shell, of material is seen out to a radius of 140". A set of eleven paraboloidal features or bow shocks may indicate clumps of fast-moving ejecta which have penetrated the decelerated shell and are generating bow shocks in the material beyond the shells. The remnant is also covered by a network of faint filamentation, the nature of which is still unclear. These may be actual filaments of compressed gas, condensed under some type of cooling or dynamical instability, or perhaps they are features of numerous intersecting shock waves propagating through the remnant.

Title:
High resolution radio maps of quasars from the Jodrell Bank 966MHz survey.
Authors:
Reid, A.; Shone, D. L.; Akujor, C. E.; Browne, I. W. A.; Murphy, D. W.; Pedelty, J.; Rudnick, L.; Walsh, D.
Publication:
Astronomy and Astrophysics Supplement, v.110, p.213 (A&AS Homepage)
Publication Date:
04/1995
Origin:
A&A KNUDSEN
A&A Keywords:
QUASARS: GENERAL, RADIO CONTINUUM: GALAXIES
Bibliographic Code:
1995A&AS..110..213R

Abstract

Radio maps are presented of quasars from the Jodrell Bank 966MHz survey. The maps are made from observations at 408MHz with MERLIN, 1464/1666MHz with the VLA/MERLIN and at 5GHz with the VLA. The core radio spectra at the three frequencies are shown for nearly all the sources, showing that although a majority of core spectra are flat, some sources have steep-spectrum cores.

Title:
The deceleration powering of synchrotron emission from ejecta components in supernova remnant Cassiopeia A
Authors:
Anderson, M. C.; Rudnick, L.
Affiliation:
AA(University of Minnesota, Minneapolis, MN, US), AB(University of Minnesota, Minneapolis, MN, US)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 441, no. 1, p. 307-333 (ApJ Homepage)
Publication Date:
03/1995
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
CASSIOPEIA A, DECELERATION, EJECTA, RADIO SOURCES (ASTRONOMY), SUPERNOVA REMNANTS, SYNCHROTRON RADIATION, ASTRONOMICAL MODELS, INTERFEROMETERS, KINEMATICS
DOI:
10.1086/175357
Bibliographic Code:
1995ApJ...441..307A

Abstract

The results of a multi-epoch radio study of secular changes in the supernova remnant (SNR) Cassiopeia A are reported and used to construct a model for the dynamical evolution of diffuse and clumpy ejecta components in the remnant. To quantify the current dynamical status of various ejecta components, the proper motions and brightness evolution of a sample of 304 compact radio features have been accurately determined from high-quality interferometric observations of the remnant at lambda = 6 and 20 cm, spanning a total time baseline of 12 yr. A simple model of homologous expansion does not provide a good fit to the measured proper motions of the radio knots. We find that a single estimate of the ejecta expansion age is not appropriate, as the expansion derived from compact features varies azimuthally and radially in the remnant and differs for subsets of knots segregated by brightness. We verify that the bulk of the radio-emitting plasma in Cas A has indeed been significantly decelerated by the current epoch; bulk expansion ages of 2.5-4 times the actual age of the remnant are measured. Based on these dynamical data, and information on the kinematics of the fast moving optical knots, we synthesize a model that directly relates the dynamics of ejecta components in Cas A to various radiative processes. This model is based on the premise that the emission from Cas A, at a variety of wavelengths, is deceleration-powered. If ejecta components are distributed over a range of internal densities, a sequential 'turning-on' of components, in order of increasing density, should be observed. A model for the current emission distribution in Cas A, at radio, X-ray, and optical wavelengths, is outlined in terms of deceleration considerations.

Title:
The polarization and depolarization of radio emission from supernova remnant Cassiopeia A
Authors:
Anderson, M. C.; Keohane, J. W.; Rudnick, L.
Affiliation:
AA(University of Minnesota, Minneapolis, MN, US), AB(University of Minnesota, Minneapolis, MN, US), AC(University of Minnesota, Minneapolis, MN, US)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 441, no. 1, p. 300-306 (ApJ Homepage)
Publication Date:
03/1995
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
CASSIOPEIA A, DEPOLARIZATION, MAGNETOHYDRODYNAMICS, POLARIZATION (WAVES), RADIO SOURCES (ASTRONOMY), SHOCK WAVES, SUPERNOVAE, ASTRONOMICAL POLARIMETRY, MAGNETIC FIELDS, RELATIVISTIC PLASMAS, SYNCHROTRON RADIATION, X RAYS
DOI:
10.1086/175356
Bibliographic Code:
1995ApJ...441..300A

Abstract

We present a study of polarimetric images of the supernova remnant Cassiopeia A at observing wavelengths of lambda = 6 and 20 cm. We find that the brigth ring is strongly depolarized at lambda = 20 cm and conclude that this is due to a mixing of the relativistic plasma responsible for the synchrotron emission and the thermal soft X-ray-emitting material behind the reverse shock. On large scales, the magnetic field is radial in Cas A, as is common in young remnants. However, the radial field region extends well beyond the bright ring, putting constraints on the field-generating mechanism. Two interesting types of small-scale features are also found and probably reflect the same underlying phenomena; the first are features at lambda = 20 cm that appear to have penetrated beyond the Faraday depolarizing shell, and the second are regions of small-scale variations in the magnetic field direction at lambda = 6 cm. Both of these are likely to be identified with moderately dense clumps of stellar ejecta, leading to the bow shocks discussed by Braun, Gull, & Perley (1987) and the evolving compact features discussed by Anderson & Rudnick (1995a).

Title:
Isolating the physical parameters of synchrotron sources
Authors:
Katz-Stone, Debora M.; Rudnick, Lawrence
Affiliation:
AA(Univ. of Minnesota, Minneapolis, MN, US), AB(Univ. of Minnesota, Minneapolis, MN, US)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 426, no. 1, p. 116-122 (ApJ Homepage)
Publication Date:
05/1994
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BRIGHTNESS DISTRIBUTION, ELECTRON ENERGY, ELECTRONS, EMISSIVITY, MAGNETIC FLUX, OPTICAL CORRECTION PROCEDURE, PARAMETER IDENTIFICATION, RADIO GALAXIES, RADIO JETS (ASTRONOMY), SYNCHROTRON RADIATION, ASTRONOMICAL MAPS, ASTRONOMICAL PHOTOMETRY, RADIO ASTRONOMY, RED SHIFT, RELATIVITY
DOI:
10.1086/174046
Bibliographic Code:
1994ApJ...426..116K

Abstract

We introduce a technique to correct synchrotron brightness maps for their dependence on observing frequency. This correction depends on the shape or 'colors' of the synchrotron spectrum and corresponds to the K-correction used for photmetry of redshifted galaxies. Using this corrected map and a spectral index map, we are able to isolate the contributions of pairs of the three physical parameters: the number of relativistic electrons along the line of sight, NT; the magnetic field strength, B; and a fiducial energy, gamma0, that characterizes the electron energy distribution. Thus by constructing maps of NT/(gamma0)2), ((gamma0)2)(B)), and NT(B) and looking for differences in the maps of these three quantities, we can, in principle, determine the parameter that dominates the emissivity for a given feature. We have applied this technique to the Carilli et al. (1991) maps of the radio galaxy Cygnus A. The resulting color-corrected map of the eastern lobe is dominated by an edge-brightened channel which straddles the counterjet, is itself girdled by rings, and is seen at low contrast in the original maps. No counterpart to this channel has yet been seen in two-dimensional or three-dimensional jet simulations. Our analysis leads us to conclude that it is dominated by a density enhancement.

Title:
Determinating which Physical Parameters Dominate the Continuum Surface Brightness in Radio Galaxies.
Authors:
Katz-Stone, Debora M.; Rudnick, Lawrence
Affiliation:
AA(University of Minnesota)
Publication:
American Astronomical Society, 184th AAS Meeting, #59.01; Bulletin of the American Astronomical Society, Vol. 26, p.957
Publication Date:
05/1994
Origin:
AAS
Abstract Copyright:
(c) 1994: American Astronomical Society
Bibliographic Code:
1994AAS...184.5901K

Abstract

The observed synchrotron brightness of sources such as radio galaxies and supernova remnants depends on the number density of relativistic electrons, their energy distribution, the distribution of magnetic field strengths and the observing frequency. We have developed a technique that can both remove the frequency dependence of the synchrotron spectrum and express the sychrotron brightness simply in terms of the total number of particles along the line-of-sight and the perpendicular component of the magnetic field. Similarly, the observed spectral index can be expressed in terms of the perpendicular componentof the magnetic field and a fiducial relativistic electron energy. Using this method, we can isolate the above physical parameters. By applying our method to VLA observations of the powerful radio galaxy, Cygnus A (Carilli et al. 1991), we find that the variations in the continuum surface brightness are primarily due to variations in the number of relativistic electrons along our line-of-sight. We also identify a prominant new feature in the eastern lobe.

Title:
A Comparison of X-ray and Radio Emission from the Supernova Remnant Cassiopeia A
Authors:
Keohane, Jonathan; Rudnick, Lawrence; Anderson, Martha
Affiliation:
AA(U of Minnesota), AB(U of Minnesota), AC(U of Minnesota)
Publication:
American Astronomical Society, 184th AAS Meeting, #56.02; Bulletin of the American Astronomical Society, Vol. 26, p.950
Publication Date:
05/1994
Origin:
AAS
Abstract Copyright:
(c) 1994: American Astronomical Society
Bibliographic Code:
1994AAS...184.5602K

Abstract

An archival ROSAT XRT/HRI image of the Cassiopeia A supernova remnant was corrected for absorption, on 30\arcsec \ (0.5 pc) scales, using existing OH and H I absorption data (Bieging & Crutcher 1986, Goss unpublished data), and theoretical effective x-ray cross-sections for the ISM. A much stronger correlation was discovered than had been previously seen between the x-ray and radio emission. We observe (log (radio))/(log (x-ray)) values between 0.26 and 0.37. The implications of these data for physical parameters in the relativistic and thermal plasmas of the supernova remnant will be discussed. Assuming the relation above, the lambda20 cm radio emission, which is free from absorption effects, was then used as a predictor of the actual x-ray emission. By comparing the predicted values to the uncorrected x-ray image, an empirical x-ray optical depth was derived. A good linear correlation exists between this empirical x-ray optical depth and the column density of hydrogen as calculated using the OH and H I absorption data. The effective cross-section of the interstellar medium was then calculated and found to be consistent with the theoretical models. This work is supported in part by NSF grant AST 9100486 to the University of Minnesota.

Title:
The Magnetic Fields of SNR CAS A and the Galaxy
Authors:
Rudnick, Lawrence; Anderson, Martha; Keohane, Jonathan
Affiliation:
AA(University of Minnesota), AB(University of Minnesota), AC(University of Minnesota)
Publication:
American Astronomical Society, 184th AAS Meeting, #56.01; Bulletin of the American Astronomical Society, Vol. 26, p.950
Publication Date:
05/1994
Origin:
AAS
Abstract Copyright:
(c) 1994: American Astronomical Society
Bibliographic Code:
1994AAS...184.5601R

Abstract

We have analyzed VLA polarization data on the supernova remnant Cas A at multiple frequencies in the lambda lambda 20cm and 6cm bands. This allows us to determine the rotation measures, depolarizations, and magnetic field orientations in the remnant. We find that the depolarization is strongly anti-correlated with the X-ray emitting shell of thermal material. The relativistic plasma, especially the bright radio ring, is therefore found mostly within the thermal shell. At the same time, a number of blobs of relativistic plasma have ``broken out'' beyond this thermal shell, and show little depolarization. However, a wide range of observed rotation measures suggests that these break-out features are still accompanied by a substantial local thermal plasma. Correcting for the rotation measures observed at high frequencies, we derive the direction of the remnant's magnetic field, and find it to be radial, to first order, as previously known. However, we find an additional, quasi-sinusoidal modulation of the field direction as a function of azimuthal angle, with an amplitude of approximately 30 degrees. This modulation can be simply modelled as due to the presence of the compressed local interstellar magnetic field within the relativistic plasma. This is not due to small scale clumps of interstellar plasma mixed with clumps of ejected plasma. Each relativistic electron actually finds itself in a local magnetic field that is the vector sum of the heavily amplified remnant field and the compressed ISM field. This result has important, but still not understood, consequences for the evolution of magnetic fields in Cas A and other supernova remnants. This work is supported in part by NSF grant AST 9100486 to the University of Minnesota.

Title:
Do relativistic electrons either gain or lose energy, outside of extragalactic nuclei?
Authors:
Rudnick, Lawrence; Katz-Stone, Debora M.; Anderson, Martha C.
Affiliation:
AA(Univ. of Minnesota, Minneapolis, MN, US), AB(Univ. of Minnesota, Minneapolis, MN, US), AC(Univ. of Minnesota, Minneapolis, MN, US)
Publication:
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 90, no. 2, p. 955-958 (ApJS Homepage)
Publication Date:
02/1994
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ELECTRON ACCELERATION, ENERGY DISSIPATION, EXTRAGALACTIC RADIO SOURCES, GALACTIC NUCLEI, RELATIVISTIC PARTICLES, ACCRETION DISKS, COMPTON EFFECT, DISTRIBUTION FUNCTIONS, ELECTRON DISTRIBUTION, LUMINOSITY, POWER SPECTRA, STOCHASTIC PROCESSES, SYNCHROTRON RADIATION
DOI:
10.1086/191931
Bibliographic Code:
1994ApJS...90..955R

Abstract

In the generally accepted models of high-luminosity extragalactic radio sources, the relativistic electron distribution evolves significantly outside of its source in the galactic nucleus; synchrotron losses occur throughout the source, and the harder (flatter) spectra seen in the hot spots are one indicator of relativistic particle acceleration. Our reanalysis and interpretation of the Carilli et al. (1991) data on Cygnus A, on the other hand, showed no evidence for evolution of the electron distribution function, and no evidence of the universally assumed injection power-law distribution. Having found a spectrum that describes an entire source, we have also introduced the technique of correcting synchrotron maps for frequency-dependent effects. In this way, a partial devonvolution of the underlying physical parameters is possible. In Cygnus A, this correction procedure led to the dominance of a hitherto unrecognized structure, an edge-brightened channel girdled by rings. We briefly discuss some implications of this work and our plans to continue this line of investigation.

Title:
The dynamical and radiative evolution of clumpy supernova ejecta
Authors:
Anderson, M. C.; Jones, T. W.; Rudnick, L.; Tregillis, I. L.; Kang, Hyesung
Affiliation:
AA(University of Minnesota, Minneapolis, MN, US), AB(University of Minnesota, Minneapolis, MN, US), AC(University of Minnesota, Minneapolis, MN, US), AD(University of Minnesota, Minneapolis, MN, US), AE(Pusan National University, Pusan, Korea)
Publication:
Astrophysical Journal, Part 2 (ISSN 0004-637X), vol. 421, no 1, p. L31-L34 (ApJ Homepage)
Publication Date:
01/1994
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
HYDRODYNAMICS, LIGHT EMISSION, MAGNETOHYDRODYNAMIC TURBULENCE, NUMERICAL ANALYSIS, PARTICLE ACCELERATION, PERTURBATION, RADIO EMISSION, SHOCK WAVES, SIGNATURES, SUPERNOVAE, THREE DIMENSIONAL MODELS, WHITE DWARF STARS, DECELERATION, EMISSIVITY, MAGNETIC FIELDS, SPACE DENSITY, TELESCOPES, VERY LARGE ARRAY (VLA), VORTICITY
DOI:
10.1086/187180
Bibliographic Code:
1994ApJ...421L..31A

Abstract

Numerical simulations describing the dynamical and radiative evolution of clumpy supernova ejecta are compared with observations of optical and radio emission knots in supernova remnant (SNR) Cassiopeia A. Three major phases are identified in the evolution of clumpy ejecta: a bow-shock phase, an instability phase, and a dispersal phase. The phenomenological and radiative signatures of each phase are discussed and compared with multi-epoch measurements of small-scale features in Cas A. Good correspondence is found between theory and observations. Both support the premise that compact radio emission features are controlled more by magnetic field amplification triggered in the instability phase than by in situ acceleration of new relativistic particles.

Title:
Spatial spectral index variations in Galactic shell supernova remnants G39.2-0.3 and G41.1-0.3
Authors:
Anderson, Martha C.; Rudnick, Lawrence
Affiliation:
AA(Minnesota Univ., Minneapolis), AB(Minnesota Univ., Minneapolis)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 408, no. 2, p. 514-529. (ApJ Homepage)
Publication Date:
05/1993
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
MILKY WAY GALAXY, PARTICLE ACCELERATION, SPECTRAL EMISSION, SUPERNOVA REMNANTS, SYNCHROTRON RADIATION, INTERSTELLAR MATTER, RADIO SPECTRA, SPATIAL DISTRIBUTION
DOI:
10.1086/172609
Bibliographic Code:
1993ApJ...408..514A

Abstract

Observations of spatial variations in the synchrotron spectra of Galactic shell SNRs G39.2-0.3 and G41.1-0.3 (3C 396 and 3C 397) are reported. Spectral indices in these remnants, as measured between 6 and 20 cm, vary on the order of Delta(alpha) of about 0.2. Comparison of G39.2-0.3 and G41.1-0.3 with seven other shell remnants exhibiting spatially varying spectral indices indicates that in the order of these remnants, brighter regions tend to be flatter. In the younger remnants, the highest emissivity regions are generally the steepest, but with notable exceptions. It is suggested that interactions between the expanding remnant and inhomogeneities in the surrounding medium may be instrumental to determining the spatial distribution of spectral indices in shell SNRs.

Title:
Determining the shape of spectra in extended radio sources
Authors:
Katz-Stone, Debora M.; Rudnick, Lawrence; Anderson, Martha C.
Affiliation:
AA(Minnesota Univ., Minneapolis), AB(Minnesota Univ., Minneapolis), AC(Minnesota Univ., Minneapolis)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 407, no. 2, p. 549-555. (ApJ Homepage)
Publication Date:
04/1993
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL SPECTROSCOPY, RADIO SOURCES (ASTRONOMY), SPECTRUM ANALYSIS, ASTRONOMICAL MODELS, COLOR-COLOR DIAGRAM, INTERSTELLAR MAGNETIC FIELDS, MAGNETIC FIELD CONFIGURATIONS, RELATIVISTIC ELECTRON BEAMS, SYNCHROTRON RADIATION
DOI:
10.1086/172536
Bibliographic Code:
1993ApJ...407..549K

Abstract

An innovative technique for determining the shape of the synchrotron spectra in extended radio sources is presented. The method involves the use of a three-frequency 'color-color' diagram that emphasizes differences in the shapes of various theoretical models. The technique was applied to multifrequency data of Cygnus A and a single spectral shape was found which appears to fit all positions in the source. The shape differs from standard models and there is no evidence that the spectrum is a power law in any frequency range. Results obtained do not indicate that postinjection relativistic particle acceleration occurs in this source. This study calls into question the nature of injected electron energy distribution and the validity of all current spectral analyses.

Title:
The Shape of the Spectra in Extended Radio Sources
Authors:
Katz-Stone, Debora; Rudnick, Lawrence; Anderson, Martha
Affiliation:
AA(University of Minnesota), AB(University of Minnesota), AC(University of Minnesota)
Publication:
American Astronomical Society, 181st AAS Meeting, #41.08; Bulletin of the American Astronomical Society, Vol. 24, p.1185
Publication Date:
09/1992
Origin:
AAS
Abstract Copyright:
(c) 1992: American Astronomical Society
Bibliographic Code:
1992AAS...181.4108K

Abstract

Using an innovative technique for displaying the sychrotron spectrum, we have found that it is possible to describe the multifrequency observations taken by Carilli et al., (1991) of Cygnus A as a single shape spectrum that is simply shifted in both ln nu and ln I possibly as a result of changes in the magnetic field throughout the source. The shape of this spectrum is curved for both low and high frequencies, i.e. a power law is not seen; it does not show preference to alpha =-.5 or alpha =-.7, i.e. an injection index is not observed. These conclusions stand in direct contrast to standard analyses, which invoke a power law injection of electrons followed by steepening due to synchrotron losses. The appropriateness of that standard model, for Cygnus A and other sources, is thus called into question. This work is funded, in part, by NSF grant AST-91-00486 to the University of Minnesota. Reference Carilli, C.L., Perley, R.A., Dreher, J.W., & Leahy, J.P., 1991 ApJ 383 544

Title:
The quest for particle acceleration in extragalactic sources
Authors:
Rudnick, Lawrence; Katz-Stone, Debora; Anderson, Martha
Affiliation:
AA(Minnesota Univ., Minneapolis), AB(Minnesota Univ., Minneapolis), AC(Minnesota Univ., Minneapolis)
Publication:
In: Particle acceleration in cosmic plasmas; Proceedings of the Workshop, Bartol Research Inst., Newark, DE, Dec. 4-6, 1991 (A93-39976 16-93), p. 424-429. (AIPC Homepage)
Publication Date:
00/1992
Category:
Space Radiation
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, PARTICLE ACCELERATION, PLASMA DIFFUSION, RELATIVISTIC PLASMAS, SHOCK WAVE INTERACTION, RADIATION SPECTRA, SYNCHROTRON RADIATION
Bibliographic Code:
1992AIPC..264..424R

Abstract

The types of observations used to study the acceleration of relativistic electrons in the diffuse plasma of extragalactic radio sources are discussed. The conditions under which such acceleration is important and which acceleration processes dominate are identified. Some of the pitfalls in such analyses are examined, and directions for future work are suggested.

Title:
Observational tests of particle acceleration theory - Shell supernova remnants
Authors:
Anderson, Martha C.; Rudnick, Lawrence
Affiliation:
AA(Minnesota Univ., Minneapolis), AB(Minnesota Univ., Minneapolis)
Publication:
In: Particle acceleration in cosmic plasmas; Proceedings of the Workshop, Bartol Research Inst., Newark, DE, Dec. 4-6, 1991 (A93-39976 16-93), p. 195-198. (AIPC Homepage)
Publication Date:
00/1992
Category:
Space Radiation
Origin:
STI
NASA/STI Keywords:
GALACTIC COSMIC RAYS, PARTICLE ACCELERATION, PARTICLE THEORY, STELLAR ENVELOPES, SUPERNOVA REMNANTS, BRIGHTNESS DISTRIBUTION, RADIO OBSERVATION, RELATIVISTIC PARTICLES
Bibliographic Code:
1992AIPC..264..195A

Abstract

Ways in which radio continuum observations of shell SNR can be applied to the study of astrophysical particle acceleration are discussed. As an example, radio observations of SNRs Cas A, G39.2-0.3, and G41.1-0.3 are presented. It is found that spatial variations in the radio spectral index, observed in several shell remnants, in conjunction with measurements of radio brightness and polarization, can provide constraints for various acceleration models.

Title:
Relativistic Electron Populations in Shell Supernova Remnants
Authors:
Anderson, M.; Rudnick, L.
Publication:
Bulletin of the American Astronomical Society, Vol. 23, p.1464
Publication Date:
09/1991
Origin:
ADS
Bibliographic Code:
1991BAAS...23.1464A

Abstract

Not Available

Title:
Relativistic electron populations in Cassiopeia A
Authors:
Anderson, M.; Rudnick, L.; Leppik, P.; Perley, R.; Braun, R.
Affiliation:
AA(Minnesota, University, Minneapolis), AB(Minnesota, University, Minneapolis), AC(Minnesota, University, Minneapolis), AD(National Radio Astronomy Observatory, Socorro, NM), AE(Netherlands Foundation for Radio Astronomy, Dwingeloo)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 373, May 20, 1991, p. 146-157. (ApJ Homepage)
Publication Date:
05/1991
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
CASSIOPEIA A, PARTICLE ACCELERATION, RADIO EMISSION, RELATIVISTIC PARTICLES, STELLAR RADIATION, SUPERNOVA REMNANTS, BRIGHTNESS DISTRIBUTION, ELECTRON ACCELERATION, RADIANT FLUX DENSITY, SPECTRAL ENERGY DISTRIBUTION, VERY LARGE ARRAY (VLA)
DOI:
10.1086/170033
Bibliographic Code:
1991ApJ...373..146A

Abstract

Spectral index variations are observed in the radio brightness distribution in the supernova remnant Cassiopeia A, between observing wavelengths of 20 and 6 cm. Reliable variations are seen over a range of -0.64 to -0.92, with steeper spectra typically associated with compact features such as the 'bow shocks' and flatter spectra with the bright radio ring. The spatial scales over which significant variations are detected range from about 11 arcsec to greater than 80 arcsec. These results indicate a direct link between the dynamics of the remnant and the relativistic particle energy distributions. Building on previously suggested dynamical pictures, it is suggested that the bow shocks are caused by moderately dense clumps of ejecta newly encountering the shocked ISM. It is found that models based on first-order Fermi acceleration in the test particle limit are unable to explain, concurrently, the steep spectral indices and the high synchrotron emissivities observed in Cas A. Thus, consideration of other types of processes, such as acceleration in cosmic-ray-mediated shocks and turbulent acceleration with secularly increasing B fields, is required.

Title:
Temporal Changes in the Spatial Distribution of Spectral Index in Cassiopeia A
Authors:
Anderson, M. C.; Rudnick, L.
Publication:
Bulletin of the American Astronomical Society, Vol. 23, p.916
Publication Date:
03/1991
Origin:
ADS
Bibliographic Code:
1991BAAS...23Q.916A

Abstract

Not Available

Title:
Relativistic Electrons and the Terminal Shock in the 3C33 North Radio Hot Spot
Authors:
Rudnick, L.; Anderson, M. C.
Publication:
Bulletin of the American Astronomical Society, Vol. 22, p.1301
Publication Date:
09/1990
Origin:
ADS
Bibliographic Code:
1990BAAS...22.1301R

Abstract

Not Available

Title:
Flow patterns in radio hot spots - A study of 3C 33 north
Authors:
Rudnick, Lawrence; Anderson, Martha
Affiliation:
AA(Minnesota, University, Minneapolis), AB(Minnesota, University, Minneapolis)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 355, June 1, 1990, p. 427-435. (ApJ Homepage)
Publication Date:
06/1990
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
FLOW DISTRIBUTION, GALACTIC STRUCTURE, RADIO GALAXIES, ASTRONOMICAL MODELS, EMISSIVITY, INTERSTELLAR MAGNETIC FIELDS
DOI:
10.1086/168776
Bibliographic Code:
1990ApJ...355..427R

Abstract

High-resolution (0.36 arcsec, 0.41 kpc) observations of the northern hot spot of the radio galaxy 3C 33 show a symmetric 'mushroom cap' structure, with a centrally placed H-shaped feature and two opposed small bright regions. Two models for the flow patterns in this hot spot are explored. The first is the 'splash' picture, in which the brightest compact feature is identified as the primary hot spot and the rest of the structures result from the jet's expanded, deflected flow. Although most observed features are consistent with this picture, they do not help discriminate against alternative models. The second, axisymmetric, picture compares the observations with numerical simulations of jets with helical magnetic fields. Good agreement was found with the geometrical and magnetic field properties, although significant questions remain about the synchrotron emissivity characteristics. The differences between the northern and southern hot spots of 3C 33 are briefly discussed, and it is suggested that there are no good explanations for these differences in the context of current models.

Title:
The Evolution of Relativistic Electrons in Cassiopeia A
Authors:
Rudnick, L.; Anderson, M.
Publication:
Bulletin of the American Astronomical Society, Vol. 22, p.833
Publication Date:
03/1990
Origin:
ADS
Bibliographic Code:
1990BAAS...22..833R

Abstract

Not Available

Title:
Spectral Index Variations in Cassiopeia A
Authors:
Anderson, M. C.; Rudnick, L.
Publication:
Bulletin of the American Astronomical Society, Vol. 22, p.751
Publication Date:
01/1990
Origin:
ADS
Bibliographic Code:
1990BAAS...22..751A

Abstract

Not Available

Title:
Strong asymmetries in the radio galaxy 3C 337 and its large-scale emission-line gas
Authors:
Pedelty, Jeffrey A.; Rudnick, Lawrence; McCarthy, Patrick J.; Spinrad, Hyron
Affiliation:
AA(Minnesota, University, Minneapolis), AB(Minnesota, University, Minneapolis), AC(California, University, Berkeley), AD(California, University, Berkeley)
Publication:
Astronomical Journal (ISSN 0004-6256), vol. 98, Oct. 1989, p. 1232-1245. (AJ Homepage)
Publication Date:
10/1989
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL SPECTROSCOPY, EMISSION SPECTRA, GALACTIC STRUCTURE, INTERSTELLAR GAS, RADIO GALAXIES, ASTRONOMICAL MAPS, ASYMMETRY, GRAY SCALE, LINE SPECTRA
DOI:
10.1086/115210
Bibliographic Code:
1989AJ.....98.1232P

Abstract

Detailed multifrequency VLA observations of the high-luminosity radio galaxy 3C 337 reveal a source that is highly asymmetric in its structural, luminosity, spectral, and polarization properties. Extensive emission-line regions are seen to the east of the galaxy, where the radio source shows signs of interaction with an external medium, such as strong depolarization and a double hotspot. These results are discussed in the context of a clumpy two-phase thermal medium around distant radio galaxies and its importance for their structure.

Title:
The Clumpy Medium Around Distant Radio Galaxies
Authors:
Pedelty, J. A.; Rudnick, L.; McCarthy, D.; Spinrad, H.
Publication:
Bulletin of the American Astronomical Society, Vol. 21, p.1093
Publication Date:
09/1989
Origin:
ADS
Bibliographic Code:
1989BAAS...21.1093P

Abstract

Not Available

Title:
The clumpy medium around distant radio galaxies
Authors:
Pedelty, Jeffrey A.; Rudnick, Lawrence; McCarthy, Patrick J.; Spinrad, Hyron
Affiliation:
AA(Minnesota, University, Minneapolis), AB(Minnesota, University, Minneapolis), AC(California, University, Berkeley), AD(California, University, Berkeley)
Publication:
Astronomical Journal (ISSN 0004-6256), vol. 97, March 1989, p. 647-665. (AJ Homepage)
Publication Date:
03/1989
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
RADIO GALAXIES, RADIO OBSERVATION, DEPOLARIZATION, EMISSION SPECTRA, GALACTIC NUCLEI, POLARIZED RADIATION, RADIO EMISSION, VERY LARGE ARRAY (VLA)
DOI:
10.1086/115011
Bibliographic Code:
1989AJ.....97..647P

Abstract

The polarization properties of distant 3C radio galaxies with strong nuclear or extended optical emission lines are studied, using radio observations at 6 and 20 cm wavelengths. Rotation-measure variations of magnitude 80-300 radians/sq m are observed on a scale size of about 10-20 kpc. It is found that the depolarization of the radio lobes is strongest when the radio emission is within about 60-100 kpc of the host-galaxy nucleus. The results imply that a clumpy Faraday medium capable of depolarizing the radio emission exists in the host-galaxy environment.

Title:
A tale of two hot spots
Authors:
Rudnick, Lawrence
Affiliation:
AA(Minnesota, University, Minneapolis)
Publication:
IN: Hot spots in extragalactic radio sources; Proceedings of the Workshop, Tegernsee, Federal Republic of Germany, Feb. 8-12, 1988 (A90-33526 14-90). Berlin and New York, Springer-Verlag, 1989, p. 61-66.
Publication Date:
00/1989
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BRIGHTNESS, EXTRAGALACTIC RADIO SOURCES, RADIO JETS (ASTRONOMY), SYNCHROTRON RADIATION, ASTRONOMICAL MAPS, BOW WAVES, MAGNETIC FIELD CONFIGURATIONS, RELATIVISTIC EFFECTS, SHOCK WAVES
Bibliographic Code:
1989LNP...327...61R

Abstract

The critical hydrodynamic and particle acceleration assumption in the standard fluid flow models of extragalactic radio sources are discussed using the two hot spots in 3C33. Details of the northern and southern hot spots in 3C33 are completely different despite strong similarties in the large scale structures. It is argued that both of the spots appear 'simple', i.e., not complicated by wandering beams or external inhomogeneities, and possible reasons for thier differences are explored. A key question is whether the relativistic particles and fields originate only within the contact discontinuity, or can be accelerated/compressed behind the bow shock as well. Coupled with this question is the ignorance of which physical parameters or features in the fluid flow correlate with synchrotron emissivity.

Title:
Fluid structures in a radio galaxy lobe - Observations of 3C 33 south
Authors:
Rudnick, Lawrence
Affiliation:
AA(Minnesota, University, Minneapolis)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 325, Feb. 1, 1988, p. 189-203. (ApJ Homepage)
Publication Date:
02/1988
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, RADIO GALAXIES, RADIO SOURCES (ASTRONOMY), ASTRONOMICAL MAPS, BOW WAVES, SYNCHROTRON RADIATION
DOI:
10.1086/165994
Bibliographic Code:
1988ApJ...325..189R

Abstract

Observations of the southern lobe of 3C 33 are presented which may provide observational confirmation for the idea that hydrodynamic considerations govern the basic appearance and structure of the leading edges of classical double sources. Apparent supersonic fluid flow features in the head of 3C 33 are identified. The head of the lobe is probably an illuminated bow shock which advances into the intergalactic medium at a Mach number of about 2.3. The synchrotron emissivity along the shock front scales with the local pressure jump as would be expected under conditions of equipartition between relativistic particles and fields. Observations of both external and internal shocks in extragalactic sources may permit a determination of the underlying physical flow parameters.

Title:
Mergers and starbursts at large redshifts - The case of 3C 368
Authors:
Djorgovski, S.; Spinrad, H.; Pedelty, J.; Rudnick, L.; Stockton, A.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AB(California, University, Berkeley), AC(Minnesota, University, Minneapolis), AD(Minnesota, University, Minneapolis), AE(Hawaii, University, Honolulu)
Publication:
Astronomical Journal (ISSN 0004-6256), vol. 93, June 1987, p. 1307-1317. Research supported by Harvard University. (AJ Homepage)
Publication Date:
06/1987
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
GALACTIC STRUCTURE, RADIO GALAXIES, RED SHIFT, STAR FORMATION, ASTRONOMICAL SPECTROSCOPY, COSMOLOGY, GALACTIC EVOLUTION, LINE SPECTRA, LUMINOSITY, MORPHOLOGY
DOI:
10.1086/114413
Bibliographic Code:
1987AJ.....93.1307D

Abstract

The results of a multiwavelength study of the high-redshift radio galaxy 3C 368, which has optical and spectroscopic properties perhaps typical of powerful 3CR galaxies at large redshifts, are reported. The galaxy's resolved, multicomponent morphology of the starlight continuum and forbidden O II 3727 A emission-line gas and the properties of the ionized-gas velocity field are suggestive of a strong and highly dissipative merger. The morphological and spectroscopic similarities with other 3CR galaxies at redshift greater than one suggest that spectacular merging was a common process in such systems at early epochs.

Title:
A different perspective on superluminal sources
Authors:
Rudnick, Lawrence
Affiliation:
AA(Minnesota, University, Minneapolis)
Publication:
IN: Superluminal radio sources; Proceedings of the Workshop, Pasadena, CA, Oct. 28-30, 1986 (A88-39751 16-90). Cambridge and New York, Cambridge University Press, 1987, p. 217-232.
Publication Date:
00/1987
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, RELATIVISTIC VELOCITY, ACTIVE GALACTIC NUCLEI, BROADBAND, LUMINOSITY, POLARIZATION (WAVES), RADIO SPECTRA, VERY LONG BASE INTERFEROMETRY
Bibliographic Code:
1987slrs.work..217R

Abstract

The ability to study and place superluminal sources in the more general context of compact radio sources, information gained from studies of broadband spectra, variability, and polarization, and a different way of looking at active nuclei are discussed in a review of the study of superluminal sources. The difficulty of studying superluminal sources is examined, presenting problems encountered in efforts to unify various aspects of research. It is suggested that a unifying regulating process is responsible for the simple broadband spectral shapes and the relations between sources, arguing that this process will probably be discovered through fundamental laws such as equilibrium, equipartition, or entropy rather than through detailed physics.

Title:
A Cautionary Note on `Cluster' Radio Sources
Authors:
Rudnick, L.; Birkinshaw, M.
Affiliation:
AB(Harvard Smithsonian Center for Astrophysics
Publication:
NRAO Greenbank Workshop 16, eds. O'Dea, C. and Uson, J., NRAO, Greenbank, WV, p. 339
Publication Date:
00/1987
Origin:
AUTHOR
Bibliographic Code:
1987nrao.work..339R

Abstract

Not Available

Title:
Active extragalactic sources - Nearly simultaneous observations from 20 centimeters to 1400 A
Authors:
Landau, Robert; Golisch, Bill; Jones, Terry J.; Jones, T. W.; Pedelty, Jeffrey; Rudnick, Lawrence; Sitko, Michael L.; Kenney, Jeff; Roellig, Tom; Salonen, Erkki; Urpo, Seppo; Schmidt, Gary; Neugebauer, Gerry; Matthews, Keith; Elias, J. H.; Impey, C.; Clegg, P.; Harris, S.
Affiliation:
AA(Minnesota, University, Minneapolis), AB(Minnesota, University, Minneapolis), AC(Minnesota, University, Minneapolis), AD(Minnesota, University, Minneapolis), AE(Minnesota, University, Minneapolis), AF(Minnesota, University, Minneapolis), AG(Minnesota, University, Minneapolis), AH(Massachusetts, University, Amherst), AI(NASA, Ames Research Center, Moffett Field, CA), AJ(Helsinki University of Technology, Espoo, Finland)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 308, Sept. 1, 1986, p. 78-92. (ApJ Homepage)
Publication Date:
09/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, EXTRAGALACTIC RADIO SOURCES, MICROWAVE SPECTRA, QUASARS, SPECTROPHOTOMETRY, DATA CORRELATION, INFRARED ASTRONOMY SATELLITE, IUE, POLARIZED ELECTROMAGNETIC RADIATION, SPECTRAL ENERGY DISTRIBUTION
DOI:
10.1086/164480
Bibliographic Code:
1986ApJ...308...78L

Abstract

IRAS, IUE, and ground-based optical, NIR, mm and submm, and radio observations obtained mainly on Apr. 9-23, 1983, are reported for 19 active extragalactic sources and eight control sources. The overall spectra of the compact active sources are shown to be well represented by continuous-curvature functions such as parabolas. The spectra are found to be consistent with models involving continuous particle injection (with synchrotron losses) or first-order Fermi acceleration (with escape and synchrotron losses), but not with models using relativistic Maxwellian electron distributions.

Title:
Weak nuclei of powerful radio sources - Spectra and polarizations
Authors:
Rudnick, L.; Jones, T. W.; Fiedler, R.
Affiliation:
AA(Minnesota, University, Minneapolis), AB(Minnesota, University, Minneapolis), AC(Minnesota, University, Minneapolis; Iowa, University, Iowa City)
Publication:
Astronomical Journal (ISSN 0004-6256), vol. 91, May 1986, p. 1011-1018. (AJ Homepage)
Publication Date:
05/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL SPECTROSCOPY, EXTRAGALACTIC RADIO SOURCES, POLARIZATION CHARACTERISTICS, SPECTRUM ANALYSIS, PERIODIC VARIATIONS, RADIANT FLUX DENSITY, SPECTRAL ENERGY DISTRIBUTION, TABLES (DATA)
DOI:
10.1086/114077
Bibliographic Code:
1986AJ.....91.1011R

Abstract

Observations are presented of the spectra and polarizations of the weak cores of extended extragalactic radio sources. These cores typically show peaked spectra, and, below a luminosity of about 10 to the 26th W/Hz, are unpolarized with 90 percent confidence upper limits of about 0.6 percent. In both of these properties the cores distinguish themselves as a class from strong, active compact sources, such as those that show superluminal motion. The relation between these weak cores and other classes of compact sources and the implications for 'unified' models based on relativistic beaming are briefly discussed. It is concluded that there is a distinct class of compact objects, different from relativistic jets, which appear in the form of separate weak or dominant cores, or as the base component in superluminal jets.

Title:
Radio and Optical Observations of the Distant Radio Galaxy 3C337 and its Extranuclear Emission-line Gas
Authors:
Pedelty, J.; Rudnick, L.; van Breugel, W.; Spinrad, H.
Publication:
Bulletin of the American Astronomical Society, Vol. 18, p.688
Publication Date:
03/1986
Origin:
ADS
Bibliographic Code:
1986BAAS...18Q.688P

Abstract

Not Available

Title:
Shock Features in a Radio Galaxy Lobe - 3C33S
Authors:
Rudnick, L.
Publication:
Bulletin of the American Astronomical Society, Vol. 18, p.689
Publication Date:
03/1986
Origin:
ADS
Bibliographic Code:
1986BAAS...18..689R

Abstract

Not Available

Title:
Radio emission in clusters - Problems and opportunities
Authors:
Rudnick, L.
Affiliation:
AA(Minnesota, University, Minneapolis)
Publication:
IN: Radio continuum processes in clusters of galaxies; Proceedings of the Workshop, Green Bank, WV, Aug. 4-8, 1986 (A88-38551 15-90). Charlottesville, VA, National Radio Astronomy Observatory, 1986, p. 1-8.
Publication Date:
00/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
GALACTIC CLUSTERS, GALACTIC EVOLUTION, RADIO EMISSION, RADIO SOURCES (ASTRONOMY), PARTICLE ACCELERATION, RADIO ASTRONOMY, RADIO GALAXIES, RELATIVISTIC PARTICLES
Bibliographic Code:
1986racp.work....1R

Abstract

The emission of radio sources in clusters of galaxies is examined in a theoretical review, with a focus on the effects of the cluster environment on the observable properties of the source. Particular attention is given to the energy source in AGN, the possible role of galaxy interactions, propagation dynamics, the need for more information on the dynamical state of the intracluster medium, relativistic particle acceleration and losses, cluster halos and steep-spectrum sources, inverse Compton scattering, Thomson scattering, and Faraday rotation.

Title:
A cautionary note on cluster radio sources.
Authors:
Rudnick, L.; Birkinshaw, M.
Publication:
NRAO Workshop, No. 16, p. 339
Publication Date:
00/1986
Origin:
ARI
Keywords:
Clusters of Galaxies:Radio Galaxies, Clusters of Galaxies:Radio Sources, Intracluster Matter:Radio Sources, Radio Galaxies:Clusters of Galaxies, Radio Sources:Clusters of Galaxies, Radio Sources:Intracluster Matter
Bibliographic Code:
1986NRAOW..16..339R

Abstract

Not Available

Title:
Radio emission in clusters: problems and opportunities.
Authors:
Rudnick, L.
Publication:
NRAO Workshop, No. 16, p. 1 - 8
Publication Date:
00/1986
Origin:
ARI
Keywords:
Clusters of Galaxies:Radio Radiation, Clusters of Galaxies:Radio Sources, Radio Radiation:Clusters of Galaxies, Radio Sources:Clusters of Galaxies
Bibliographic Code:
1986NRAOW..16....1R

Abstract

Not Available

Title:
Evidence for a universal, simple model for active extragalactic sources.
Authors:
Jones, T. W.; Rudnick, L.; Landau, R.
Publication:
Continuum emission in active galactic nuclei, p. 122 - 133
Publication Date:
00/1986
Origin:
ARI
Keywords:
Active Galactic Nuclei:Continuum Radiation, Active Galactic Nuclei:Models
Bibliographic Code:
1986ceangwork..122J

Abstract

Not Available

Title:
Evidence for a universal, simple model for active extragalactic sources
Authors:
Jones, T. W.; Rudnick, L.; Landau, R.
Affiliation:
AA(Minnesota, University, Minneapolis), AB(Minnesota, University, Minneapolis), AC(Minnesota, University, Minneapolis)
Publication:
IN: Continuum emission in active galactic nuclei; Proceedings of the Workshop, Tucson, AZ, January 11-14, 1986 (A87-21576 07-90). Cincinnati, OH, University of Cincinnati, 1986, p. 122-133.
Publication Date:
00/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL MODELS, EXTRAGALACTIC RADIO SOURCES, GALACTIC NUCLEI, GALACTIC RADIATION, SPECTRUM ANALYSIS, ACTIVE GALACTIC NUCLEI, CONTINUOUS RADIATION, MILLIMETER WAVES, POLARIZATION (WAVES)
Bibliographic Code:
1986ceagnwork..122J

Abstract

The spectra of 27 active galactic nuclei, measured at up to 24 wavelengths between 20 cm and 1400 A during the spring of 1983, are examined. Of these sources, 15, chosen either for strong millimeter emission or, in three cases, because they were highly polarized optical sources, form a remarkably homogeneous group. The peak frequency of the log normal curves are concentrated around 5 x 10 to the 13th Hz in the source rest frame, while a strong inverse correlation exists between the width of the curve and the bolometric luminosity. These results encourage one to look for a single controlling parameter in attempting to define the behavior of active sources.

Title:
Broad-band polarization observations of active compact radio sources
Authors:
Rudnick, L.; Jones, T. W.; Fiedler, R. L.; Aller, H. D.; Aller, M. F.; Hodge, P. E.; Owen, F. N.; Bignell, R. C.; Puschell, J. J.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN), AC(Iowa, University, Iowa City, IA; Minnesota, University, Minneapolis, MN), AD(Michigan, University, Ann Arbor, MI), AE(Michigan, University, Ann Arbor, MI), AF(Maryland, University, Baltimore, MD; Michigan, University, Ann Arbor, MI), AG(National Radio Astronomy Observatory, Socorro, NM), AH(National Radio Astronomy Observatory, Socorro, NM), AI(Titan Systems, San Diego, CA)
Publication:
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 57, April 1985, p. 693-709. (ApJS Homepage)
Publication Date:
04/1985
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
INTERSTELLAR MAGNETIC FIELDS, POLARIMETRY, POLARIZATION CHARACTERISTICS, RADIO SOURCES (ASTRONOMY), VERY LONG BASE INTERFEROMETRY, BROADBAND, RADIANT FLUX DENSITY, TABLES (DATA)
DOI:
10.1086/191023
Bibliographic Code:
1985ApJS...57..693R

Abstract

Simultaneous multifrequency linear polarimetry data between 1.4 and 90 GHz were obtained for about 20 active, compact radio sources for six epochs between December 1977 and July 1980. A presentation is made of the total flux density results for fifth and sixth sessions, a summary of all polarization observations, and a description of the observational and analytical procedure. An inference is made that it is useful to decompose the observed polarizations from each source into a 'common' vector component, which appears to be related to the VLBI structural angle and a stochastic vector component which varies in both frequency and time.

Title:
Magnetic field structures in active compact radio sources
Authors:
Jones, T. W.; Rudnick, L.; Fiedler, R. L.; Aller, H. D.; Aller, M. F.; Hodge, P. E.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN), AC(Minnesota, University, Minneapolis, MN), AD(Michigan, University, Ann Arbor, MI), AE(Michigan, University, Ann Arbor, MI), AF(Michigan, University, Ann Arbor, MI)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 290, March 15, 1985, p. 627-636. (ApJ Homepage)
Publication Date:
03/1985
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, INTERSTELLAR MAGNETIC FIELDS, MAGNETIC FIELD CONFIGURATIONS, POLARIMETRY, ANISOTROPIC MEDIA, RANDOM WALK, TIME DEPENDENCE, WAVELENGTHS
DOI:
10.1086/163020
Bibliographic Code:
1985ApJ...290..627J

Abstract

The analysis of simultaneous multifrequency linear polarimetry data between 1.4 GHz and 90 GHz for about 20 active, compact radio sources at six epochs from 1977 December 10 1980 July is presented. In addition, monthly 8 Ghz polarization data on the same sources were examined. The general polarization characteristics of these sources can be well described in terms of magnetic fields which are largely turbulent and slightly anisotropic. The magnetic field symmetry axes are generally aligned with the source structural axes on the milli-arcsecond scale (OJ 287 is a notable exception.) Monte Carlo calculations indicate that observed polarization variations and in particular 'rotator' polarization events can be produced in this model as a consequence of 'random walks' generated through evolution of the turbulent magnetic field.

Title:
Optical and radio polarimetry of the quasar 0846 + 513
Authors:
Sitko, M. L.; Rudnick, L.; Jones, T. W.; Schmidt, G. D.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN), AC(Minnesota, University, Minneapolis, MN), AD(Steward Observatory, Tucson, AZ)
Publication:
Astronomical Society of the Pacific, Publications (ISSN 0004-6280), vol. 96, June 1984, p. 402-405. (PASP Homepage)
Publication Date:
06/1984
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, POLARIMETRY, QUASARS, INTERSTELLAR MAGNETIC FIELDS, LIGHT EMISSION, POLARIZATION CHARACTERISTICS, RADIANT FLUX DENSITY, RADIO SPECTRA
Bibliographic Code:
1984PASP...96..402S

Abstract

Recent observations of polarization of the violent variable quasar 0846 + 513 are presented. Observations of this object confirm that it is a highly polarized, highly variable quasar. It is found that while the position angle of the plane of polarization may remain very steady for extended periods of time, it is not constant. The observations place useful constraints on the source size, magnetic field strength, the presence of beaming, and the probable spectral shape in the unobserved spectral region between 2 microns and 2 cm.

Title:
The nature of radio-quiet QSOs-VLA observations of 0026 + 129, 0205 + 024, and 1351 + 640
Authors:
Rudnick, L.; Sitko, M. L.; Stein, W. A.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN), AC(Minnesota, University, Minneapolis, MN)
Publication:
Astronomical Journal (ISSN 0004-6256), vol. 89, June 1984, p. 753-757. (AJ Homepage)
Publication Date:
06/1984
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL MAPS, QUASARS, RADIO ASTRONOMY, ASTRONOMICAL COORDINATES, BROADBAND, EMISSION SPECTRA, RED SHIFT, SEYFERT GALAXIES
DOI:
10.1086/113572
Bibliographic Code:
1984AJ.....89..753R

Abstract

VLA maps of 'radio-quiet' QSOs are reported. Extended emission is found on linear scales of about 10 kpc, larger than that observed in Seyfert galaxies, but smaller than most radio-loud objects. The spectral properties of some radio-quiet objects are also very similar to those of radio-quiet Seyfert galaxies such as NGC 4151; some radio-quiet QSOs are probably just luminous Seyfert galaxies. There is no sign of either external or self-absorption of a radio-loud core. Thermal gas suppression due to the emission-line material cold mask the appearance of a very compact core. However, unlike their radio-loud counterparts, the radio-quiet QSOs must not eject large numbers of relativistic particles over scales larger than that of the emission-line gas. The ejection trigger may be the primary discriminant between radio-loud and radio-quiet QSOs, and may be luminosity-related.

Title:
Alternating-side ejection in extragalactic radio sources
Authors:
Rudnick, L.; Edgar, B. K.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 279, April 1, 1984, p. 74-85. (ApJ Homepage)
Publication Date:
04/1984
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL MAPS, EJECTA, EXTRAGALACTIC RADIO SOURCES, GALACTIC STRUCTURE, ASYMMETRY, GALACTIC NUCLEI, PARTICLE ACCELERATION, QUASARS, RELATIVISTIC PARTICLES
DOI:
10.1086/161866
Bibliographic Code:
1984ApJ...279...74R

Abstract

Analyses of radio galaxy and QSO maps provide evidence for a preferential avoidance of structures at the same nuclear distance on the two sides of a source. It is shown that such an effect is most likely due to ejections from the nucleus occurring on only one side at a time. Under this model, strict constraints are placed on the ejection velocities, the amount of 'cold' material carried along with the relativistic electrons, and the power supply to jets and hot spots. Some theoretical difficulties raised by this model are discussed, referring to current ideas about forming one-sided sources. The lack of a clear signature in other observational tests is demonstrated, and future work is suggested. Throughout the paper, the very limited nature in which extragalactic radio sources are symmetric is emphasized.

Title:
Stochastic Stokes Formation and Rotations in Compact Extragalactic Sources
Authors:
Rudnick, L.; Jones, T. W.; Aller, H. D.; Aller, M. F.
Publication:
Bulletin of the American Astronomical Society, Vol. 16, p.461
Publication Date:
03/1984
Origin:
ADS
Bibliographic Code:
1984BAAS...16..461R

Abstract

Not Available

Title:
BL Lac's rotation measure
Authors:
Rudnick, L.; Jones, T. W.; Edgar, B. K.; Pedelty, J. A.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN), AC(Minnesota, University, Minneapolis, MN), AD(Minnesota, University, Minneapolis, MN)
Publication:
Astronomical Journal (ISSN 0004-6256), vol. 89, March 1984, p. 316-318. (AJ Homepage)
Publication Date:
03/1984
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, EXTRAGALACTIC RADIO SOURCES, POLARIZATION CHARACTERISTICS, ROTATION, ANGULAR DISTRIBUTION, WAVELENGTHS
DOI:
10.1086/113514
Bibliographic Code:
1984AJ.....89..316R

Abstract

The rotation measure of the rapid variable source BL Lac has been determined by simultaneous polarization measurements at two sets of four closely spaced wavelengths. The derived value of - 198 + - 4 rad/sq m is consistent with data over at least the last decade, while the source has had a variety of intrinsic position angles. The rotation measure is also similar to those of other extragalactic sources and pulsars near its position lII = 90 deg, bII = - 10 deg.

Title:
Vortex rings in extended doubles
Authors:
Rudnick, L.
Publication:
Physics of Energy Transport in Extragalactic Radio Sources, Proceedings of NRAO Workshop no.9, held at Green Bank, West Virginia, July 30th - August 3rd, 1984. Edited bY Alan H. Bridle. Green Bank: National Radio Astronomy Observatory, 1984., p.182
Publication Date:
00/1984
Origin:
ADS
Bibliographic Code:
1984pete.conf..182R

Abstract

Not Available

Title:
The Jolly Green Jet (EVENING DEMONSTRATION)
Authors:
Rudnick, L.
Publication:
Physics of Energy Transport in Extragalactic Radio Sources, Proceedings of NRAO Workshop no.9, held at Green Bank, West Virginia, July 30th - August 3rd, 1984. Edited bY Alan H. Bridle. Green Bank: National Radio Astronomy Observatory, 1984., p.133
Publication Date:
00/1984
Origin:
ADS
Bibliographic Code:
1984pete.conf..133R

Abstract

Not Available

Title:
Jet speed
Authors:
Rudnick, L.
Publication:
Physics of Energy Transport in Extragalactic Radio Sources, Proceedings of NRAO Workshop no.9, held at Green Bank, West Virginia, July 30th - August 3rd, 1984. Edited bY Alan H. Bridle. Green Bank: National Radio Astronomy Observatory, 1984., p.114
Publication Date:
00/1984
Origin:
ADS
Bibliographic Code:
1984pete.conf..114R

Abstract

Not Available

Title:
Pieces of jets and other thoughts on flip-flops
Authors:
Rudnick, L.
Publication:
Physics of Energy Transport in Extragalactic Radio Sources, Proceedings of NRAO Workshop no.9, held at Green Bank, West Virginia, July 30th - August 3rd, 1984. Edited bY Alan H. Bridle. Green Bank: National Radio Astronomy Observatory, 1984., p.35
Publication Date:
00/1984
Origin:
ADS
Bibliographic Code:
1984pete.conf...35R

Abstract

Not Available

Title:
Measurement of unambiguous rotation measures of extragalactic sources
Authors:
Rudnick, L.; Zukowski, E.; Kronberg, P. P.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Scarborough College; David Dunlap Observatory, West Hill, Ontario, Canada), AC(Scarborough College; David Dunlap Observatory, West Hill, Ontario, Canada)
Publication:
Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 52, May 1983, p. 317-321. Sponsorship: Natural Sciences and Engineering Research Council. (A&AS Homepage)
Publication Date:
05/1983
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, FARADAY EFFECT, GALACTIC ROTATION, LINEAR POLARIZATION, ASTRONOMICAL CATALOGS, RADIO ASTRONOMY
Bibliographic Code:
1983A&AS...52..317R

Abstract

The results are reported of polarization measurements conducted specifically to check for the existence of very high Faraday rotation measures, which might otherwise have been undetected. Polarization measurements are presented for 24 extragalactic radio sources at 4 contiguous bands around 9 cm, from observations at the NRAO 300 ft. telescope. It is shown how these measurements can be used to derive rotation measures (and limits) which are free from n pi phase ambiguities around 9 cm. It is found that the data can not be made consistent with arbitrarily large rotation measures. Revised rotation measures and initial position angles are presented for the observed sources.

Title:
Rotation measures for compact variable radio sources
Authors:
Rudnick, L.; Jones, T. W.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN)
Publication:
Astronomical Journal (ISSN 0004-6256), vol. 88, April 1983, p. 518-526. (AJ Homepage)
Publication Date:
04/1983
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, FARADAY EFFECT, POLARIZED ELECTROMAGNETIC RADIATION, BL LACERTAE OBJECTS, CENTIMETER WAVES, HISTOGRAMS, VERY LARGE ARRAY (VLA)
DOI:
10.1086/113337
Bibliographic Code:
1983AJ.....88..518R

Abstract

Rotation measures for 31 compact variable extragalactic sources using Very Large Array observations at 18 cm and 20.5 cm wavelengths have been derived. Polarization and total intensity data are presented for these and 29 additional sources at 6 cm and 2 cm wavelengths, as well. Maps are also presented for sources with confusing extended structure. The calculated rotation measures are distributed similarly to those of extended sources, and do not appear to change over about 7 years (using data from Wardle 1977). The intrinsic polarization position angles of compact sources are shown to be similar over wide separations in wavelength. The implications for the magnetic fields in and around compact sources are briefly discussed.

Title:
Polarizations of Compact Extragalactic Sources Over 2 Decades in Frequency
Authors:
Rudnick, L.; Jones, T. W.; Aller, H.; Aller, M.; Hodge, P.; Bignell, R. C.; Owen, F. N.; Puschell, J. J.
Publication:
Bulletin of the American Astronomical Society, Vol. 15, p.648
Publication Date:
03/1983
Origin:
ADS
Bibliographic Code:
1983BAAS...15Q.648R

Abstract

Not Available

Title:
Observations of the Jet in 3C33. 1
Authors:
Edgar, B. K.; Rudnick, L.
Publication:
Bulletin of the American Astronomical Society, Vol. 15, p.657
Publication Date:
03/1983
Origin:
ADS
Bibliographic Code:
1983BAAS...15..657E

Abstract

Not Available

Title:
Luminosity and Spectral Shape Effects in Compact Radio Sources
Authors:
Pedelty, J. A.; Rudnick, L.; Jones, T. W.
Publication:
Bulletin of the American Astronomical Society, Vol. 15, p.648
Publication Date:
03/1983
Origin:
ADS
Bibliographic Code:
1983BAAS...15..648P

Abstract

Not Available

Title:
Simultaneous visual-infrared polarimetry of QSOs
Authors:
Puschell, J. J.; Jones, T. W.; Phillips, A. C.; Simpson, E.; Sitko, M.; Rudnick, L.; Stein, W. A.; Moneti, A.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN), AC(Minnesota, University, Minneapolis, MN), AD(Minnesota, University, Minneapolis, MN), AE(Minnesota, University, Minneapolis, MN)
Publication:
Astrophysical Journal, Part 1, vol. 265, Feb. 15, 1983, p. 625-631. (ApJ Homepage)
Publication Date:
02/1983
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
INFRARED ASTRONOMY, POLARIMETRY, QUASARS, FARADAY EFFECT, OPTICAL POLARIZATION, WAVELENGTHS
DOI:
10.1086/160708
Bibliographic Code:
1983ApJ...265..625P

Abstract

The possible causes of the wavelength-dependent polarization found in simultaneous visual and IR polarimetry of several QSOs are considered. Faraday rotation inside 0754+101 can explain the data only if one invokes multiple spectral domains, or spectral components with differing polarization properties. Detailed observations of the evolution of wavelength - dependent polarization are needed to test these models, and it is expected that an understanding of the wavelength dependence of polarization will provide significant information about conditions in the core regions which produce the visual-IR continuum in QSOs.

Title:
Optical and radio structure of the quasar PKS 0812 + 02
Authors:
Wyckoff, S.; Johnston, K.; Ghigo, F.; Rudnick, L.; Wehinger, P.; Boksenberg, A.
Publication:
Astrophysical Journal, Part 1, vol. 265, Feb. 1, 1983, p. 43-50. (ApJ Homepage)
Publication Date:
02/1983
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
DIFFUSE RADIATION, GALACTIC NUCLEI, GALACTIC RADIATION, LIGHT EMISSION, QUASARS, RADIO GALAXIES, BRIGHTNESS DISTRIBUTION, GALACTIC CLUSTERS, GALACTIC STRUCTURE, LINEAR POLARIZATION, NONTHERMAL RADIATION, RADIANT FLUX DENSITY, RADIO SPECTRA, VISIBLE SPECTRUM
DOI:
10.1086/160652
Bibliographic Code:
1983ApJ...265...43W

Abstract

VLA observations of the quasar PKS 0812 + 02 (z = 0.402) have resolved it into three components: (1) a flat spectrum radio source coinciding with the quasar; (2) a northwest radio lobe which is resolved into two components separated by 0.6 arcsec along P.A. of approximately 70 deg with an overall spectral index of -1.0; and (3) a diffuse component of size 25 x 8 arcsec at a wavelength of 6 cm with a spectral index of -0.6. It is noted that the high ratio of peak surface brightness between the two lobes of the radio source and the extensive low brightness emission are unusual for quasars. The northwest radio lobe coincides with a diffuse optical object with a surface brightness of approximately 23.7 mag/sq arcsec. The low-resolution spectrum of the northwest object may indicate a dominant nonthermal emission source. It is concluded that if the northwest radio lobe and optical object are physically associated this would be one of the first detections of optical emission from a quasar radio lobe.

Title:
The Optical-Radio Morphology of the SW Lobe in 3C33
Authors:
Dreher, J. W.; Simkin, S. M.; Rudnick, L.; Saslaw, W.; Tyson, A.; Crane, P.
Publication:
Bulletin of the American Astronomical Society, Vol. 14, p.933
Publication Date:
09/1982
Origin:
ADS
Bibliographic Code:
1982BAAS...14..933D

Abstract

Not Available

Title:
Compact radio sources - The dependence of variability and polarization on spectral shape
Authors:
Rudnick, L.; Jones, T. W.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN)
Publication:
Astrophysical Journal, Part 1, vol. 255, Apr. 1, 1982, p. 39-47. (ApJ Homepage)
Publication Date:
04/1982
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
LINE SHAPE, POLARIZATION CHARACTERISTICS, QUASARS, RADIO SOURCES (ASTRONOMY), BL LACERTAE OBJECTS, DEPOLARIZATION, FARADAY EFFECT
Comment:
A&AA ID. AAA031.141.045
DOI:
10.1086/159800
Bibliographic Code:
1982ApJ...255...39R

Abstract

The polarization properties and variability of a sample of flat-spectrum compact radio sources have been investigated. An unbiased sample of 40 sources selected from the S4 (6-cm strong source) survey was observed at 20, 6 and 2 cm by the VLA, and flux variability was estimated by comparison with the original survey results. Observations reveal significant differences in flux variability and polarization characteristics between sources of different spectral shapes. Those with straight spectra are noted to be small in comparison with steeper-spectrum sources, are not variable and show evidence for Faraday depolarization, possibly corresponding to transparent sources confined within a galaxy. Sources with simple convex spectral shapes vary only slightly and have small polarizations which are similar between frequencies; they may be interpreted by nonpower-law electron distributions. Complex sources are highly variable and show considerable scatter between fractional polarizations at different wavelengths, very similar to the strong millimeter active sources.

Title:
Broadband Studies of Compact Sources
Authors:
Jones, T.; Rudnick, L.
Publication:
EXTRAGALACTIC RADIO SOURCES: I.A.U. SYMP.97 1982 P.329, 1982
Publication Date:
00/1982
Origin:
KNUDSEN
Comment:
A&AA ID. AAA031.141.172
Bibliographic Code:
1982IAUS...97..329J

Abstract

Not Available

Title:
Nuclear ejection - One side at a time
Authors:
Rudnick, L.
Affiliation:
AA(Minnesota, University, Minneapolis, MN)
Publication:
In: Extragalactic radio sources; Proceedings of the Symposium, Albuquerque, NM, August 3-7, 1981. (A82-47855 24-90) Dordrecht, D. Reidel Publishing Co., 1982, p. 47-49.
Publication Date:
00/1982
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASYMMETRY, EXTRAGALACTIC RADIO SOURCES, NUCLEAR PARTICLES, PARTICLE EMISSION, ASTRONOMICAL MODELS, EJECTION, HISTOGRAMS, NUCLEAR RADIATION, RADIO ASTRONOMY
Comment:
A&AA ID. AAA031.141.112
Bibliographic Code:
1982IAUS...97...47R

Abstract

The present investigation is concerned with aspects of asymmetry in extragalactic radio sources. General symmetries have been found in extragalactic radio sources. However, when examined in detail, most double sources are very different on the two sides. It is pointed out that these differences are of a very specific nature. Namely, when emission is found on one side of a source, there is generally not emission at the same distance on the other side; where one side turns on, the other side turns off. This on/off property may well apply to all extragalactic sources, but is seen in its extreme in one-sided jets and in the D2 sources. The implications of these findings are examined. There must be some coordination or physical relation between events on each side of a source, so that they can avoid occurring at the same distance from the nucleus. Possibilities regarding such a relation or coordination are considered.

Title:
VLA and optical mapping of the quasar PKS 0812+020
Authors:
Ghigo, F. D.; Rudnick, L.; Johnston, K. J.; Wehinger, P. A.; Wyckoff, S.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Minnesota, University, Minneapolis, MN), AC(U.S. Navy, Naval Research Laboratory, Washington, DC), AD(Arizona State University, Tempe; Northern Arizona University, Flagstaff, AZ), AE(Arizona State University, Tempe, AZ)
Publication:
In: Extragalactic radio sources; Proceedings of the Symposium, Albuquerque, NM, August 3-7, 1981. (A82-47855 24-90) Dordrecht, D. Reidel Publishing Co., 1982, p. 43, 44. Research supported by the European Southern Observatory and Max-Planck Gesellschaft zur Foerderung der Wissenschaften
Publication Date:
00/1982
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL MAPS, EMISSION SPECTRA, GALACTIC CLUSTERS, QUASARS, RADIO SPECTRA, VISIBLE SPECTRUM, ANTENNA ARRAYS, ASTRONOMICAL SPECTROSCOPY, BRIGHTNESS DISTRIBUTION, RADIANT FLUX DENSITY
Comment:
A&AA ID. AAA031.141.110
Bibliographic Code:
1982IAUS...97...43G

Abstract

Not Available

Title:
3C129 - another Case of Precessing Beams
Authors:
Rudnick, L.; Burns, J.; Icke, V.
Publication:
SKY AND TELESCOPE V. 62, P. 318, 1981 (S&T Homepage)
Publication Date:
10/1981
Origin:
KNUDSEN
Bibliographic Code:
1981S&T....62..318R

Abstract

Not Available

Title:
3C 129 close-up
Authors:
Rudnick, L.; Burns, J. O.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(New Mexico, University, Albuquerque, NM)
Publication:
Astrophysical Journal, Part 2 - Letters to the Editor, vol. 246, June 1, 1981, p. L69-L72. Research supported by the U.S. Department of Energy (ApJ Homepage)
Publication Date:
06/1981
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
GALACTIC STRUCTURE, PLASMA JETS, RADIO GALAXIES, RADIO SOURCES (ASTRONOMY), ANTENNA ARRAYS, ASTRONOMICAL MODELS, GALACTIC NUCLEI, INTERGALACTIC MEDIA, RELATIVISTIC PLASMAS, SUPERSONIC FLOW
Comment:
A&AA ID. AAA029.141.189
DOI:
10.1086/183555
Bibliographic Code:
1981ApJ...246L..69R

Abstract

High-resolution VLA observations of the head-tail radio galaxy 3C 129 have shown thin, faint streams connecting the nucleus to the larger tails. The multiple bends and wiggles in the source are easily described in terms of precessing beams, as shown in a companion Letter by Icke (1981). As in NGC 1265, the jets can be mildly supersonic or mildly relativistic. The major features of these curved streams and their importance for general models of extragalactic jets are pointed out.

Title:
The radio/optical emission in 3C 33 south
Authors:
Rudnick, L.; Saslaw, W. C.; Crane, P.; Tyson, J. A.
Affiliation:
AA(Minnesota, University, Minneapolis, MN), AB(Virginia, University, Charlottesville, VA; National Radio Astronomy Observatory, Green Bank, WV; Cambridge University, Cambridge, England), AC(European Southern Observatory, Garching, West Germany), AD(Bell Telephone Laboratories, Inc., Murray Hill, NJ)
Publication:
Astrophysical Journal, Part 1, vol. 246, June 15, 1981, p. 647-652. (ApJ Homepage)
Publication Date:
06/1981
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
LIGHT EMISSION, RADIO EMISSION, RADIO GALAXIES, ASTRONOMICAL MAPS, BRIGHTNESS DISTRIBUTION, CONTOURS, RADIO ASTRONOMY, SYNCHROTRON RADIATION, THERMAL ABSORPTION, THERMAL EMISSION, VERY LARGE ARRAY (VLA)
Comment:
A&AA ID. AAA029.141.194
DOI:
10.1086/158961
Bibliographic Code:
1981ApJ...246..647R

Abstract

The southern lobe of 3C 33 has been observed with the Very Large Array at wave lengths of 6 cm and 2 cm and resolutions 1 arcsec. The results clearly demonstrate a physical association between the radio source and the optical patch found by Simkin (1978). The spectral index shows that the optical emission could be the synchrotron tail of the radio radiation, provided that the lobe is continually supplied with relativistic particles with gamma not less than 10 to the 6th. If thermal gas is responsible for the optical emission, these radio polarization observations show that it must be well separated from the relativistic material. The ionization and thermal balance of any thermal gas pose a number of interesting problems. Several critical observations for future work are identified.

Title:
Detailed Maps of a Quasar with a Radio Jet and with Optical Emission in One of its Radio Lobes
Authors:
Ghigo, F. D.; Rudnick, L.; Wehinger, P. A.; Wyckoff, S.
Publication:
Bulletin of the American Astronomical Society, Vol. 13, p.530
Publication Date:
03/1981
Origin:
ADS
Comment:
A&AA ID. AAA030.141.059
Bibliographic Code:
1981BAAS...13R.530G

Abstract

Not Available

Title:
The broad-band spectra and variability of compact nonthermal sources
Authors:
Jones, T. W.; Rudnick, L.; Owen, F. N.; Puschell, J. J.; Ennis, D. J.; Werner, M. W.
Affiliation:
AA(Minnesota, University, Minneapolis, Minn.), AB(Minnesota, University, Minneapolis, Minn.), AC(National Radio Astronomy Observatory, Charlottesville, Va.), AD(National Radio Astronomy Observatory, Charlottesville, Va.), AE(Palomar Observatory, Pasadena, Calif.), AF(Palomar Observatory, Pasadena, Calif.)
Publication:
Astrophysical Journal, Part 1, vol. 243, Jan. 1, 1981, p. 97-107. Research supported by the University of Minnesota (ApJ Homepage)
Publication Date:
01/1981
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EXTRAGALACTIC RADIO SOURCES, INFRARED ASTRONOMY, NONTHERMAL RADIATION, RADIO SPECTRA, SPECTRAL LINE WIDTH, ENERGY SPECTRA, GALACTIC NUCLEI, INFRARED SPECTRA, MILLIMETER WAVES, VARIABILITY, VISIBLE SPECTRUM
Comment:
A&AA ID. AAA029.141.052
DOI:
10.1086/158571
Bibliographic Code:
1981ApJ...243...97J

Abstract

It is noted that in approximately a dozen sources, nearly simultaneous infrared and/or visual spectra are available, making it possible to examine the relationship between the infrared-visual and radio regimes. A simple transition to the steeper infrared spectra is seen as likely with a mean break wavelength of approximately 300 microns in the rest frame. These observations indicate a tapered source geometry, with the smallest structures roughly on the order of 10 to the 16th cm as estimated from the spectral break; this is consistent with scales estimated from optical variability time scales. Large amplitude variations on a six-month time interval are found to be fairly infrequent in most of the sources. A relatively model-independent way of categorizing flux variations as due to changes in source scale, or structure or the slope of the electron energy spectrum is suggested.

Title:
The behavior of hot spots in classical double radio sources
Authors:
Neff, S. G.; Rudnick, L.
Affiliation:
AA(Virginia, University, Charlottesville, Va.), AB(National Radio Astronomy Observatory, Green Bank, W. Va.)
Publication:
Royal Astronomical Society, Monthly Notices, vol. 192, Aug. 1980, p. 531-544. (MNRAS Homepage)
Publication Date:
08/1980
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BINARY STARS, EXTRAGALACTIC RADIO SOURCES, STELLAR LUMINOSITY, STELLAR STRUCTURE, BRIGHTNESS TEMPERATURE, CORRELATION COEFFICIENTS, DATA PROCESSING, RED SHIFT, STOCHASTIC PROCESSES, SURFACE PROPERTIES, VOID RATIO
Comment:
A&AA ID. AAA028.141.002
Bibliographic Code:
1980MNRAS.192..531N

Abstract

The relationship between the structure and luminosity of strong extragalactic radio sources (reported by Jenkins & McEllin) and between the source structure and redshift is shown to be largely an effect of observing the sources with unequal linear resolutions. Weak trends still exist after statistical correction for resolution effects, but they are dominated by inter- and intra-source scatter. At 5-km resolution, the fraction of total flux which comes from 'hot spots' of high surface brightness could be dependent on some as-yet-undetermined source characteristics, or it could be caused by some short-lived stochastic process that is unrelated in detail to general source properties.

Title:
The Radio/Optical Structure of the QSO 0812+020
Authors:
Wyckoff, S.; Johnston, K.; Ghigo, F.; Rudnick, L.; Wehinger, P.; Gehren, T.; Boksenberg, A.
Publication:
Bulletin of the American Astronomical Society, Vol. 12, p.497
Publication Date:
03/1980
Origin:
ADS
Comment:
A&AA ID. AAA028.141.041
Bibliographic Code:
1980BAAS...12..497W

Abstract

Not Available

Title:
Broadband Spectra and Variability of Compact Nonthermal Sources
Authors:
Rudnick, L.; Jones, T. W.; Owen, F. N.; Puschell, J. J.; Ennis, D. J.;