Comparison of positions and magnitudes of asteroids observed in the sloan digital sky survey with those predicted for known asteroids

We positionally correlate known asteroids with a sample of ∼18,000 asteroids detected by the Sloan Digital Sky Survey (SDSS). We find 2641 unique matches, which represent the largest sample of asteroids with both accurate multicolor photometry and known orbital parameters. The matched objects are predominantly bright and demonstrate that the SDSS photometric pipeline recovers ∼90% of the known asteroids in the observed region. For the recovered asteroids, we find a large offset (∼0.4 mag) between Johnson V magnitudes derived from SDSS photometry and the predicted magnitudes. This offset varies with the asteroid color, from 0.34 mag for blue asteroids to 0.44 mag for red asteroids, and is probably caused by the use of unfiltered CCD observations in the majority of recent asteroid surveys. This systematic photometric error leads to an overestimate of the number of asteroids brighter than a given absolute magnitude limit by a factor of ∼1.7. The distribution of the matched asteroids in orbital parameter space indicates strong color segregation. We confirm that some families are dominated by a single asteroid type (e.g., the Koronis family by red asteroids and the Themis family by blue asteroids), while others appear to be a mixture of blue and red objects (e.g., the Nysa-Polana family). Asteroids with the bluest i*-z* colors, which can be associated with the Vesta family, show particularly striking localization in orbital parameter space.