The Cornell High-Order Adaptive Optics Survey for Brown Dwarfs in Stellar Systems. II. Results from Monte Carlo Population Analyses

In this second of a two-paper sequence, we present Monte Carlo populationsimulation results of brown dwarf companion data collected during the CornellHigh-order Adaptive Optics Survey for brown dwarf companions (CHAOS). Makingreasonable assumptions of orbital parameters (random inclination, randomeccentricity and random longitude of pericentre) and age distributions, andusing published mass functions, we find that the brown dwarf companion fractionaround main sequence stars is 0.0%-9.3% for the 25-100 AU semi-major axisregion. We find a corresponding L-dwarf companion fraction of 0.0%-3.3%. Wecompare our population analysis methods and results with techniques and resultspresented by several other groups. In this comparison we discover thatsystematic errors (most notably resulting from orbital projection effects)occur in the majority of previously published brown dwarf companion populationestimates, leading authors to claim results not supported by the observationaldata.Comment: Accepted for publication in the Astronomical Journal. 21 pages including 4 figures and 1 tabl