THE CALTECH WIDE AREA SKY SURVEY Beyond (50000) Quaoar

The first phase of the Caltech Wide Area Sky Survey occurred from late November 2001 through mid-April 2003. We present preliminary results from this survey which has detected 28 bright Kuiper Belt Objects (KBOs) and 4 Centaurs, 19 of which were discovered in our survey including Quaoar, the largest KBO, as well as 6 of the 10 intrinsically brightest KBOs. We have surveyed 5108 square degrees of the sky nearest the invariable plane to a limiting red magnitude of 20.7. Correcting for the overabundance of objects near the invariable plane, this represents 27% completeness in terms of KBO numbers. Thus, approximately 100 KBOs and Centaurs brighter than mR = 20.7 exist, about 3/4 of which remain undiscovered. The bright KBOs are consistent with the canonical q = 4 size distribution, suggesting that about ten 1000 km diameter KBOs and about one 2000 km diameter KBO exist. Additionally, we observe only 3 KBOs with low inclination (i < 7 degrees) with 67% of the sky available to these objects surveyed. This is in sharp contrast with the known KBOs, of which about 60% of the ∼ 800 observed objects (as of May 2003) have i < 7 degrees. Although we observe at systematically higher invariable plane latitudes than many deeper KBO surveys, such systematic biases cannot fully explain the lack of low inclination objects, a measurement which is significant at the > 3σ level. This suggests that the bright KBOs have a fundamentally different maximum size than the fainter KBOs. A better characterization of the survey limiting magnitude and a more thorough modeling of observational bias effects of different classes of KBOs will be made in a future work.