ALMA observations of rho-Oph 102: grain growth and molecular gas in the
  disk around a young Brown Dwarf
  We present ALMA continuum and spectral line observations of the young Brown
Dwarf rho-Oph 102 at about 0.89 mm and 3.2 mm. We detect dust emission from the
disk at these wavelengths and derive an upper limit on the radius of the dusty
disk of ~ 40 AU. The derived variation of the dust opacity with frequency in
the mm provides evidence for the presence of mm-sized grains in the disk outer
regions. This result demonstrates that mm-grains are found even in the low
density environments of Brown Dwarf disks and challenges our current
understanding of dust evolution in disks. The CO map at 345 GHz clearly reveals
molecular gas emission at the location of the Brown Dwarf, indicating a
gas-rich disk as typically found for disks surrounding young pre-Main Sequence
stars. We derive a disk mass of ~ 0.3-1% of the mass of the central Brown
Dwarf, similar to the typical values found for disks around more massive young
stars.
