A search for pre- and proto-brown dwarfs in the dark cloud Barnard 30 with ALMA

TL;DR

This study uses ALMA observations to identify and characterize the lowest mass objects, including potential pre-brown dwarfs, in the Barnard 30 dark cloud, revealing five unresolved sources with masses down to planetary scales.

Contribution

First ALMA continuum survey of Barnard 30 identifying potential pre-brown dwarf cores and low-mass stars, providing insights into the earliest stages of substellar object formation.

Findings

Detected five unresolved sources with ALMA, masses between 0.9 and 67 M$_{ m Jup}$.

Two sources show gas emission consistent with rotating disks or envelopes.

Three sources lack infrared counterparts, possibly representing starless cores or deeply embedded objects.

Abstract

In this work we present ALMA continuum observations at 880 $\mu$m of 30 sub-mm cores previously identified with APEX/LABOCA at 870$\mu$m in the Barnard 30 cloud. The main goal is to characterize the youngest and lowest mass population in the cloud. As a result, we report the detection of five (out of 30) spatially unresolved sources with ALMA, with estimated masses between 0.9 and 67 M$_{\rm Jup}$. From these five sources, only two show gas emission. The analysis of multi-wavelength photometry from these two objects, namely B30-LB14 and B30-LB19, is consistent with one Class II- and one Class I low-mass stellar object, respectively. The gas emission is consistent with a rotating disk in the case of B30-LB14, and with an oblate rotating envelope with infall signatures in the case of LB19. The remaining three ALMA detections do not have infrared counterparts and can be classified as either deeply embedded objects or as starless cores if B30 members. In the former case, two of them (LB08 and LB31) show internal luminosity upper limits consistent with Very Low Luminosity objects, while we do not have enough information for LB10. In the starless core scenario, and taking into account the estimated masses from ALMA and the APEX/LABOCA cores, we estimate final masses for the central objects in the substellar domain, so they could be classified as pre-BD core candidates.