Brown dwarf disks with ALMA

TL;DR

This study uses ALMA data to analyze three brown dwarf disks, revealing their large sizes, dust grain growth to millimeter sizes, and implications for planet formation around very low mass objects.

Contribution

First detailed ALMA observations of brown dwarf disks showing their size, structure, and dust properties, extending understanding of disk evolution in very low mass systems.

Findings

Disks are relatively large with radii around 70 AU.

Dust grains have grown to at least millimeter sizes.

Solid growth occurs similarly as in disks around more massive stars.

Abstract

We present ALMA continuum and spectral line data at 0.89 mm and 3.2 mm for three disks surrounding young brown dwarfs and very low mass stars in the Taurus star forming region. Dust thermal emission is detected and spatially resolved for all the three disks, while CO(J=3-2) emission is seen in two disks. We analyze the continuum visibilities and constrain the disks physical structure in dust. The results of our analysis show that the disks are relatively large, the smallest one with an outer radius of about 70 AU. The inferred disk radii, radial profiles of the dust surface density and disk to central object mass ratios lie within the ranges found for disks around more massive young stars. We derive from our observations the wavelength dependence of the millimeter dust opacity. In all the three disks data are consistent with the presence of grains with at least millimeter sizes, as also found for disks around young stars, and confirm that the early stages of the solid growth toward planetesimals occur also around very low mass objects. We discuss the implications of our findings on models of solids evolution in protoplanetary disks, on the main mechanisms proposed for the formation of brown dwarfs and very low mass stars, as well as on the potential of finding rocky and giant planets around very low mass objects.