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CfA</title></head><body>
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<div><font color="#000000">TUESDAY, DECEMBER 2<br>
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4:20 pm:</font><font color="#6B4226"> Graduate Student Research
Forum</font><font color="#000000">. "Deep Searches for Kuiper
Belt Objects," Dr. Matthew Holman, CfA. Preceded by refreshments.
Phillips Auditorium.</font><br>
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<div><font color="#000000"><i>Abstract</i>: Since the planetesimals in
extrasolar systems are too faint to see with present or planned
telescopes, the Kuiper Belt is our best chance to test models of
accretional/collisional evolution against observations. Last February,
Bernstein et al. (2003) conducted a survey of 6 HST ACS/WFC fields
(0.02 sq. deg.) to detect KBOs as faint as magnitude R = 28.7,
corresponding to diameters as small as D=25 km. While roughly 85
detections were expected from a simple extrapolation of the luminosity
function at brighter magnitudes, only three new Kuiper belt objects
were discovered, indicating a significant break in an otherwise power
law distribution of sizes. Such a break has been seen in numerical
simulations of the collisional evolution of the Kuiper belt (Davis and
Farinella 1997; Kenyon and Luu 1999). Despite the depth of the HST/ACS
search, the limited number of known KBOs in the magnitude range 25 <
R < 27 leaves the location of the break in the size distribution
poorly constrained. With the availability of Megacam on the MMT and
IMACS on Magellan we are now in a position to conduct deep searches
for KBOs to better establish the size distribution in this magnitude
range.</font></div>
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