A submillimetre search for pre- and proto-brown dwarfs in Chamaeleon II

Gregorio-Monsalvo, I. de; Barrado, D.; Bouy, H.; Bayo, A.; Palau, Aina; Morales-Calderón, M.; Huélamo, N.; Morata, Ó.; Merın, Bruno; Eiroa, C.

doi:10.1051/0004-6361/201424149

Cited by 10 publications

(10 citation statements)

References 39 publications

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“…So far, the only confirmed pre-BD is Oph B-11 (André et al 2012) and there are pre-BD candidates both in Taurus (Palau et al 2012;Tokuda et al 2019) and Barnard 30 (Huélamo et al 2017;Barrado et al 2018). Regarding proto-BDs, one excellent Class 0/I candidate has been identified in Perseus (Palau et al 2014) and other candidates are proposed in Taurus (Apai et al 2005;Barrado et al 2009;Palau et al 2012;Morata et al 2015;Dang-Duc et al 2016), Chamaeleon II (de Gregorio-Monsalvo et al 2016), Ophiuchus (Whelan et al 2018;Riaz et al 2018;Kawabe et al 2018), Serpens (Riaz et al 2016(Riaz et al , 2018, and σ Orionis (Riaz et al 2015(Riaz et al , 2017(Riaz et al , 2019, although many of these may also be more evolved Class I objects. Finally, the search and study of very low luminosity objects (VeLLOs) have revealed sources that show proto-BD characteristics (Bourke et al 2006;Lee et al 2009Lee et al , 2013Lee et al , 2018Kauffmann et al 2011;Kim et al 2019; also see the references in Table 4 of Palau et al 2014).…”

Section: Introductionmentioning

confidence: 99%

ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds

Santamaría-Miranda

Gregorio-Monsalvo

Plunkett

et al. 2021

A&A

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Context. The dominant mechanism leading to the formation of brown dwarfs (BDs) remains uncertain. While the census of Class II analogs in the substellar domain continues to grow, the most direct keys to formation, which are obtained from younger objects (pre-BD cores and proto-BDs), are limited by the very low number statistics available. Aims. We aim to identify and characterize a set of pre-and proto-BDs as well as Class II BDs in the Lupus 1 and 3 molecular clouds to test their formation mechanism. Methods. We performed ALMA band 6 (1.3 mm) continuum observations of a selection of 64 cores previously identified from AzTEC/ASTE data (1.1 mm), along with previously known Class II BDs in the Lupus 1 and 3 molecular clouds. Surveyed archival data in the optical and infrared were used to complement these observations. We expect these ALMA observations prove efficient in detecting the youngest sources in these regions, since they probe the frequency domain at which these sources emit most of their radiation. Results. We detected 19 sources from 15 ALMA fields. Considering all the pointings in our observing setup, the ALMA detection rate was ∼23 % and the derived masses of the detected sources were between ∼0.18 and 124 M Jup. We classified these sources according to their spectral energy distribution as 5 Class II sources, 2 new Class I/0 candidates, and 12 new possible pre-BD or deeply embedded protostellar candidates. We detected a promising candidate for a Class 0/I proto-BD source (ALMA J154229.778-334241.86) and inferred the disk dust mass of a bona fide Class II BD. The pre-BD cores might be the byproduct of an ongoing process of large-scale collapse. The Class II BD disks follow the correlation between disk mass and the mass of the central object that is observed at the low-mass stellar regime. Conclusions. We conclude that it is highly probable that the sources in the sample are formed as a scaled-down version of low-mass star formation, although disk fragmentation may be responsible for a considerable fraction of BDs.

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Section: Introductionmentioning

confidence: 99%

ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds

Santamaría-Miranda

Gregorio-Monsalvo

Plunkett

et al. 2021

A&A

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“…We can compare our results in B30 with those from two regions with very different properties: Chamaeleon II (Cha II, see de Gregorio-Monsalvo et al 2016) and the B213-L1495 clouds in Taurus (B213 hereafter Palau et al 2012;Morata et al 2015). Unlike B30, these are low-mass star forming regions that lack massive stars, and therefore do not suffer from the strong and ionizing winds associated to hot, massive objects.…”

Section: General Discussion and Conclusionmentioning

confidence: 78%

“…However, the envelope masses of FHCs are too large so it seems unlikely that they will remain substellar (see Table 4 in Palau et al 2014). Finally, observational studies using a multi-wavelength approach have provided several proto-BD candidates in different clouds and star forming regions Lee et al 2009Lee et al , 2013Kauffmann et al 2011;André et al 2012;Palau et al 2012Palau et al , 2014Morata et al 2015;Liu et al 2016;Riaz et al 2016;de Gregorio-Monsalvo et al 2016;Huélamo et al 2017). Despite these efforts, the number of proto-BD candidates is still very small and the characterization incomplete.…”

Section: Arxiv:171206399v1 [Astro-phsr] 18 Dec 2017mentioning

confidence: 99%

Early phases in the stellar and substellar formation and evolution

Barrado¹,

Gregorio-Monsalvo²,

Huélamo³

et al. 2018

A&A

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Aims. The early evolutionary stage of brown dwarfs are not very well characterized, specially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and brown dwarfs. Methods. We have conducted deep observations at 870 µm obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter 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 (SEDs) 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 submillimeter sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified in three distinct groups. First, 15 out of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BDs 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 brown dwarf 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 (YSOs), eight proto-BD candidates (with another three dubious cases), and one Very Low Luminosity objects (VeLLO). Conclusions. Our findings provide additional evidence concerning the brown dwarf formation mechanism, which seems to be a downsized version of the stellar formation.

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“…It may be possible that BDs form from core collapse, similar to higher-mass stars (see, e.g., André et al 2014; Riaz et al 2014;Lomax et al 2015). However, their masses are below or close to the Jeans mass in star-forming regions (e.g., Palau et al 2014;de Gregorio-Monsalvo et al 2016). Another formation mechanism may be the gravitational fragmentation of circumstellar disks, and numerical simulations suggest that this is indeed possible (e.g., Stamatellos & Whitworth 2009a, 2009bTsukamoto et al 2013;Forgan et al 2015;Dong et al 2016).…”

Section: Introductionmentioning

confidence: 99%

“…It may be possible that brown dwarfs form from core collapse, similar to higher-mass stars (see, e.g., André et al 2014;Riaz et al 2014;Lomax et al 2015). However, their masses are below or close to the Jeans mass in star forming regions (e.g., Palau et al 2014;de Gregorio-Monsalvo et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The Long-Term Dynamical Evolution of Disk-Fragmented Multiple Systems in the Solar Neighborhood

Kouwenhoven

Stamatellos

et al. 2016

ApJ

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The origin of very low-mass hydrogen-burning stars, brown dwarfs (BDs), and planetary-mass objects (PMOs) at the low-mass end of the initial mass function is not yet fully understood. Gravitational fragmentation of circumstellar disks provides a possible mechanism for the formation of such low-mass objects. The kinematic and binary properties of very low-mass objects formed through disk fragmentation at early times (<10 Myr) were discussed in our previous paper. In this paper we extend the analysis by following the long-term evolution of diskfragmented systems up to an age of 10 Gyr, covering the ages of the stellar and substellar populations in the Galactic field. We find that the systems continue to decay, although the rates at which companions escape or collide with each other are substantially lower than during the first 10 Myr, and that dynamical evolution is limited beyond 1 Gyr. By t=10 Gyr, about one third of the host stars are single, and more than half have only one companion left. Most of the other systems have two companions left that orbit their host star in widely separated orbits. A small fraction of companions have formed binaries that orbit the host star in a hierarchical triple configuration. The majority of such double-companion systems have internal orbits that are retrograde with respect to their orbits around their host stars. Our simulations allow a comparison between the predicted outcomes of disk fragmentation with the observed low-mass hydrogen-burning stars, BDs, and PMOs in the solar neighborhood. Imaging and radial velocity surveys for faint binary companions among nearby stars are necessary for verification or rejection of the formation mechanism proposed in this paper.

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A submillimetre search for pre- and proto-brown dwarfs in Chamaeleon II

Cited by 10 publications

References 39 publications

ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds

ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds

Early phases in the stellar and substellar formation and evolution

The Long-Term Dynamical Evolution of Disk-Fragmented Multiple Systems in the Solar Neighborhood

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