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Optical data

I am the PI of an asteroid survey which has been completed with the Large Binocular Telescope during Science Demonstration Time in January 2007. This survey looked at 4 fields centered on 0 degrees, 5 degrees, 10 degrees and 15 degrees ecliptic latitude and each field covered 0.28 square degrees. This program was very successful in characterizing the number density of asteroids as a function of ecliptic latitude and in discovering new asteroids. This data was used in my 2nd year project and will be published early in 2008. An example of this data is seen in the banner for this webpage.

Due to the success of this survey, additional data was obtained at the LBT in October 2007. Telescope availability allowed us to complete the survey 2 times, with an additional third coverage of data obtained at 15 degrees latitude. Reduction and analysis of this data is ongoing.

Infrared data

In my time at the Spitzer Science Center prior to graduate school, I joined the Spitzer Ecliptic First Look Survey (EFLS) Team. The EFLS surveyed two fields at 0 and 5 degrees latitude to determine the density of asteroids as seen in Spitzer data. I was a co-I on the resulting ApJ Supplement article and have continued to do my own analysis on the data whilst at Minnesota which resulted in a poster at the 2006 DPS meeting. I have continued with asteroid detections in IRAC data in the SWIRE Legacy program's XMM_LSS field and in the Taurus Legacy program. My dissertation will include IRAC and MIPS asteroid detections and calculated albedos and sizes for known asteroids in the Legacy programs of Taurus, SWIRE, MIPSGAL, MIPSGALII and SCOSMOS.

In my third year of graduate school I have returned to the Spitzer Science Center as a member of the MIPSGAL Legacy team. While working with the MIPSGAL team I am developing software which will automate asteroid detection in multi-epoch data and will cross reference these detections with known asteroids. This software will significantly reduce the time needed for asteroid detection and cataloging and will allow me to find all the asteroids in the relatively large multi-epoch data sets in a timely fashion. Additional software is being written to determine heliocentric and apparent distances for unknown asteroids for albedo and diameter calulations in an attempt to draw constraints on the bulk main belt size-frequency distribution and the size distribution of asteroids as a function of ecliptic latitude.

Preliminary results based on 1/5 of the MIPSGAL area (approximately 5 square degrees) allow us to obtain albedos and sizes for approximately 100 total asteroids at ecliptic latitudes of 0, 5, 10 and 15 degrees. The absolute H magnitudes of these asteroids as reported by Horizons is used in conjunction with the Standard Thermal Model of Lebofsky and Spencer (1989) for the albedo calculation. Plans for the final paper include use and comparision of results from both STM and NEATM for the whole survey. Shown below are the preliminary plots of the asteroid albedo and diameter distributions as derived using the initial 5 square degrees of data.

The peak in the number of asteroids at albedos of 0.1 which corresponds to a carbonaceous composition is not expected, we expected a distribution with a more bimodal appearance. With further analysis we will determine if this enhancement is real, or is a bias in size and albedo given by the limiting flux of MIPS observations. Preliminary analysis using known asteroids selected at 8 microns with the IRAC instrument (which has a significantly deeper flux limit) do suggest that the skew towards carbonaceous compositions at small diameters may indeed be a real effect.

The MIPSGAL Asteroid Catalog and the associated journal article will be submitted by October 2008. For preliminary results from the whole survey, please view the two posters I have presented at the 2008 summer AAS and ACM meetings below.

To test the validity of diameter and albedo fits made only with 24 micron data, I have used observations from the Taurus Legacy survey as a testing sample. The Taurus survey was designed such that IRAC and MIPS observations occured within ~ 1 week, which means that the changes in heliocentric and Spitzer distances of the asteroids were less than 0.1 AU, allowing us to compare the IRAC and MIPS results without any weighting. Our preliminary analysis with ~100 asteroids shows that fits done with IRAC channels 3 and 4 and MIPS 24 micron give albedo results within 8 percent of those derived with MIPS 24 micron only. This is within the nominal 10 percent photometry error with MIPS 24 micron observations, so we can assume that the fits with only 24 micron are relatively good. The IRAC only albedo fits however are approximately 40% different than those derived with all wavelength data available. This implies that using only IRAC data is unreliable and should not be used for any high precision estimates of diameter or albedo. Two examples are given below. In the plots, the dotted lines are the IRAC only fits, the dashe lines are the MIPS only fits and the dot-dashed lines are the combined IRAC and MIPS thermal fits.





Posters from various meetings

2008 American Astronomical Society meeting poster on the MIPSGAL survey

2008 Asteroids, Comets and Meteors conference poster on the MIPSGAL asteroid survey

2008 Division of Planetary Sciences Poster on the asteroids detected at 24 micron from the MIPSGAL and Taurus surveys

2009 American Astronomical Society meeting poster on the Taurus survey asteroids and diameters and albedos from IRAC and MIPS data