A Disk Census for Young Brown Dwarfs

Recent surveys have identified substellar objects down to planetary masses in nearby star-forming regions. Reliable determination of the disk frequency in young brown dwarfs is of paramount importance to understanding their origin. Here we report the results of a systematic study of infrared L-band (3.8 μm) disk excess in ~50 spectroscopically confirmed objects near and below the substellar boundary in several young clusters. Our observations, using the ESO Very Large Telescope, Keck I, and the NASA Infrared Telescope Facility, reveal that a significant fraction of brown dwarfs harbor disks at a very young age. Their inner disk lifetimes do not appear to be vastly different from those of disks around T Tauri stars. Our findings are consistent with the hypothesis that substellar objects form via a mechanism similar to solar-mass stars.