Disk Masses and Dust Evolution of Protoplanetary Disks Around Brown Dwarfs

Abstract

We present the largest sample of brown dwarf (BD) protoplanetary disk spectral energy distributions modeled to date. We compile 49 objects with ALMA observations from four star-forming regions: ρ Ophiuchus, Taurus, Lupus, and Upper Scorpius. Studying multiple regions with various ages enables us to probe disk evolution over time. Specifically, from our models we obtain values for dust grain sizes, dust settling, and disk mass; we compare how each of these parameters vary between the regions. We find that disk mass decreases with age. We also find evidence of disk evolution (i.e., grain growth and significant dust settling) in all four regions, indicating that planet formation and disk evolution may begin to occur at earlier stages. We generally find these disks contain too little mass to form planetary companions, though we cannot rule out that planet formation may have already occurred. Finally, we examine the disk mass -host mass relationship and find that BD disks are largely consistent with previously-determined relationships for disks around T Tauri stars.

Demographics of young stars and their protoplanetary disks: lessons learned on disk evolution and its connection to planet formation

“…6), mainly due to the intrinsic scatter in any single region and the large age difference between regions. The relation between the disk dust mass and M in individual regions holds also when including brown dwarfs in the samples (Testi et al 2016;Ward-Duong et al 2018b;Sanchis et al 2021;Rilinger and Espaillat 2021), although with hints of deviations that should be checked when larger samples of BDs become available.…”