Evidence for a Color Dependence in the Size Distribution of Main-Belt Asteroids

We present the results of a project to detect small (~1 km) main-belt asteroids with the 3.6 m Canada-France-Hawaii Telescope. We observed in two filters (MegaPrime g' and r') in order to compare the results in each band. Owing to the observational cadence we did not observe the same asteroids through each filter and thus do not have true color information. However, strong differences in the size distributions as seen in the two filters point to a color dependence at these sizes, perhaps to be expected in this regime, in which asteroid cohesiveness begins to be dominated by physical strength and composition rather than by gravity. The best-fit slopes of the cumulative size distributions (CSDs) in both filters tend toward lower values for smaller asteroids, consistent with the results of previous studies. In addition to this trend, the size distributions seen in the two filters are distinctly different, with steeper slopes in r' than in g'. Breaking our sample up according to semimajor axis, the difference between the filters in the inner belt is found to be somewhat less pronounced than in the middle and outer belt, but the CSD of those asteroids seen in the r' filter is consistently and significantly steeper than in g' throughout. The CSD slopes also show variations with semimajor axis within a given filter, particularly in r'. We conclude that the size distribution of main-belt asteroids is likely to be color-dependent at kilometer sizes and that this dependence may vary across the belt.

[1]  E. Bertin,et al.  SExtractor: Software for source extraction , 1996 .

[2]  Kevin R. Housen,et al.  Scale Effects in Strength-Dominated Collisions of Rocky Asteroids , 1999 .

[3]  P. Farinella,et al.  Fragment ejection velocities and the collisional evolution of asteroids , 1994 .

[4]  B. Efron.  The jackknife, the bootstrap, and other resampling plans , 1987 .

[5]  Edward F. Tedesco,et al.  The Infrared Space Observatory Deep Asteroid Search , 2002 .

[6]  Daisuke Kinoshita,et al.  Size and Spatial Distributions of Sub-km Main-Belt Asteroids ∗ , 2003 .

[7]  Doug Tody,et al.  The Iraf Data Reduction And Analysis System , 1986, Astronomical Telescopes and Instrumentation.

[8]  P. Farinella,et al.  The asteroids as outcomes of catastrophic collisions , 1982 .

[9]  R. Greenberg,et al.  The collisional and dynamical evolution of the main-belt and NEA size distributions , 2005 .

[10]  Robert Jedicke,et al.  Collisional Models and Scaling Laws: A New Interpretation of the Shape of the Main-Belt Asteroid Size Distribution☆ , 1998 .

[11]  J. Munn,et al.  The USNO-B Catalog , 2002, astro-ph/0210694.

[12]  C. J. van Houten,et al.  Survey of Asteroids. , 1958 .

[13]  J. S. Dohnanyi.  Collisional model of asteroids and their debris , 1969 .

[14]  J. Carvano,et al.  Distribution of taxonomic classes in the main belt of asteroids ? ? Based on observations made with , 2003 .

[15]  Joseph A. Burns,et al.  Dynamical Evolution of Main Belt Meteoroids: Numerical Simulations Incorporating Planetary Perturbations and Yarkovsky Thermal Forces , 2000 .

[16]  A. D. Dubyago,et al.  The determination of orbits. , 1961 .

[17]  P. Farinella,et al.  Modelling the outcomes of high-velocity impacts between small solar system bodies , 1993 .

[18]  E. Tedesco,et al.  Compositional Structure of the Asteroid Belt , 1982, Science.

[19]  Eugene A. Magnier,et al.  The Elixir System: Data Characterization and Calibration at the Canada‐France‐Hawaii Telescope , 2004 .

[20]  D. Padgett,et al.  Asteroid Trails in Hubble Space TelescopeWFPC2 Images: First Results☆☆☆ , 1998 .

[21]  Paolo Farinella,et al.  Asteroid collisional evolution: results from current scaling algorithms , 1994 .

[22]  T. Teichmann,et al.  Fundamentals of celestial mechanics , 1963 .

[23]  T. Nakamura,et al.  Basic nature of sub-km main-belt asteroids: their size and spatial distributions , 2004 .

[24]  R. Greenberg,et al.  Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength , 2003, 1407.3307.

[25]  K. Holsapple,et al.  On the fragmentation of asteroids and planetary satellites , 1990 .

[26]  R. Jedicke,et al.  The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids , 1998 .

[27]  Richard P. Binzel,et al.  Asteroid spectroscopy: Progress and perspectives , 1993 .

[28]  Z. Ivezic,et al.  Solar system objects observed in the Sloan Digital Sky Survey commissioning data , 2001 .

[29]  S. Dermott,et al.  The Collisional Evolution of the Asteroid Belt and Its Contribution to the Zodiacal Cloud , 1997 .

[30]  W. Benz,et al.  Catastrophic Disruptions Revisited , 1999 .

[31]  Alberto Cellino,et al.  The size distribution of main-belt asteroids from IRAS data , 1991 .