Alexander SCHOLZ : University of Toronto

The Dusty Disks of Young Brown Dwarfs: New Results from Spitzer and IRAM

Young brown dwarfs appear to share many similarities with T Tauri stars. Specifically, many of them exhibit excess emission at infrared and submm wavelengths, indicating the presence of dusty disks. Investigating the properties and evolution of these disks by analyzing their SEDs is a useful probe of brown dwarf origins, and additionally allows us to study the processes of grain and planetesimal growth in an extreme case, constraining the efficiency and universality of planet formation. Until recently, our detailed knowledge of substellar disks relied on a few case studies. Therefore we carried out a program to characterize disks of brown dwarfs based on large object samples using the unique capabilities of Spitzer combined with sensitive submm/mm observations. Our 1.3 mm study in Taurus provided MIR-mm SEDs for 20 brown dwarfs, allowing us for the first time to constrain disk masses and radii for these objects in a systematic way (Scholz, Jayawardhana & Wood, ApJ, in press). From our results, we do not see evidence for truncated disks due to an ejection process early in the life history of brown dwarfs, implying that most sub-stellar objects probably form in isolation. Additionally, we present a Spitzer IRS-MIPS study of 36 brown dwarfs in Upper Scorpius, with ages of ~5 Myr, ideal for probing disk evolution. At this age, the disks of brown dwarfs are either flat or undetectable, suggesting that processes like dust settling and inner disk clearing occur rapidly. In this talk, I will summarize both projects and present a comprehensive view of brown dwarf disks.