The large-scale disk fraction of brown dwarfs in the Taurus cloud as measured with Spitzer

TL;DR

This study measures the disk fraction of brown dwarfs in the Taurus cloud using Spitzer data, finding similarities with stars and analyzing their spatial distribution relative to molecular gas.

Contribution

It provides the first large-scale measurement of brown dwarf disk fraction in Taurus and compares it with stars, including spatial distribution analysis relative to molecular gas.

Findings

BD disk fraction is 41% ± 12%, similar to T Tauri stars.

Rare transition disks observed among BDs.

BDs are located in regions with similar molecular gas density as stars.

Abstract

Aims. The brown dwarf (BD) formation process has not yet been completely understood. To shed more light on the differences and similarities between star and BD formation processes, we study and compare the disk fraction among both kinds of objects over a large angular region in the Taurus cloud. In addition, we examine the spatial distribution of stars and BD relative to the underlying molecular gas Methods. In this paper, we present new and updated photometry data from the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope on 43 BDs in the Taurus cloud, and recalculate of the BD disk fraction in this region. We also useed recently available CO mm data to study the spatial distribution of stars and BDs relative to the cloud's molecular gas. Results. We find that the disk fraction among BDs in the Taurus cloud is 41 \pm 12%, a value statistically consistent with the one among TTS (58 \pm 9%). We find that BDs in transition from a state where they have a disk to a diskless state are rare, and we study one isolated example of a transitional disk with an inner radius of \approx 0.1 AU (CFHT BD Tau 12, found via its relatively small mid-IR excess compared to most members of Taurus that have disks. We find that BDs are statistically found in regions of similar molecular gas surface density to those associated with stars. Furthermore, we find that the gas column density distribution is almost identical for stellar and substellar objects with and without disks.