A Herschel Search for Cold Dust in Brown Dwarf Disks: First Results

We report initial results from a Herschel program to search for far-infrared emission from cold dust around a statistically significant sample of young brown dwarfs. The first three objects in our survey are all detected at 70 mu m, and we report the first detection of a brown dwarf at 160 mu m. The flux densities are consistent with the presence of substantial amounts of cold dust in the outer disks around these objects. We modeled the spectral energy distributions (SEDs) with two different radiative transfer codes. We find that a broad range of model parameters provide a reasonable fit to the SEDs, but that the addition of our 70 mu m, and especially the 160 mu m, detection enables strong lower limits to be placed on the disk masses since most of the mass is in the outer disk. We find likely disk masses in the range of a few x 10(-6) to 10(-4) M(circle dot). Our models provide a good fit to the SEDs and do not require dust settling.