Early phases in the stellar and substellar formation and evolution

Infrared and submillimeter data in the Barnard 30 dark cloud^★

¹ Depto. Astrofísica, Centro de Astrobiología (INTA-CSIC), ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Spain
e-mail: barrado@cab.inta-csic.es
² European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
³ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
⁴ Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile
⁵ Millennium Nucleus “Núcleo Planet Formation”, Universidad de Valparaíso, Chile
⁶ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, P.O. Box 3-72, 58090 Morelia, Michoacán, Mexico
⁷ Depto. de Astronomía, Universidad de Chile, Camino del Observatorio 1515, Santiago, Chile
⁸ European Space Astronomy Centre (ESA), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
⁹ Institute of Astronomy and Astrophysics, Academia Sinica, 11F of AS/NTU Astronomy-Mathematics Building, No. 1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan
¹⁰ Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA
¹¹ Depto. Física Teórica, Fac. de Ciencias, Universidad Autónoma de Madrid, Campus Cantoblanco, 28049 Madrid, Spain
¹² Unidad Asociada UAM-CAB/CSIC, Madrid, Spain
¹³ Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA

Received: 9 December 2015
Accepted: 11 November 2017

Abstract

Aims. The early evolutionary stage of brown dwarfs (BDs) is not very well characterized, especially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and BDs.

Methods. We have conducted deep observations at 870 μm obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter (submm) sources in the Barnard 30 dark cloud. We have complemented these data with multi-wavelength observations from the optical to the far-IR and compiled complete spectral energy distributions in order to identify the counterparts, characterize the sources and to assess their membership to the association and stellar or substellar status based on the available photometric information.

Results. We have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified into three distinct groups. First, 15 of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BD candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include BD candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70 μm, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects, eight proto-BD candidates (with another three dubious cases), and one very low luminosity objects.

Conclusions. Our findings provide additional evidence concerning the BD formation mechanism, which seems to be a downsized version of the stellar formation.