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Main Belt Asteroids

Main Belt Asteroid Observations

The plots below show data on Main Belt Asteroids, based on KBO search observations by David Jewitt taken at CFHT with the CFH12K Feb, 1999. These observations were 180 second images in R, spaced by roughly 1.25 hours. The total area of the observations was 3.34 square degrees (13 fields, but only 9 chips used). Objects in the images were detected with Dophot (limit of 5 sigma peak). Asteroid candidates were identified as singly detected objects which are co-linear in X,Y,T to within 1 arcsec. Figure 1 shows the velocity, magnitude distribution for the detected objects. Region B is taken to be the collection of main belt asteroids (0.01 deg / hour is ~0.6 arcsec / minute, consistent with the main belt). Region A is taken to represent the false positive detection rate. The sample in region B was used to construct the black histogram in Figure 2, while region A was used to construct the red (false-positives) histogram. The solid line is a fit to the data in the magnitude range 17 - 21.5, and the thin lines are suggested upper and lower limits. Integrating these three fits, I find that, if we can extrapolate from 22 to 24 mag, the surface density of main-belt objects with R < 24 will be in the range of 120 - 300 objects per square degree, with a best fit of 200 per square degree.

Figure 1

Figure 2

postscript versions of these plots:

apparent magnitude distribution
velocity-magnitude diagram

A text table of the asteroid astrometry.

This page is maintained by Eugene Magnier