Substellar Objects in Nearby Young Clusters (Sonyc). Iv. A Census of Very Low Mass Objects in NGC 1333

Scholz, Alexander; Mužić, Koraljka; Geers, Vincent; Bonavita, M.; Jayawardhana, Ray; Tamura, Motohide

doi:10.1088/0004-637x/744/1/6

Cited by 85 publications

(50 citation statements)

References 65 publications

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“…For these spectral indices we conclude that results for objects with SpT in the nominal range of validity of each index are reliable within a typical uncertainty of about one subclass. A good correlation is also found for the spectral index Scholz et al (2012) spectral index from the literature, we obtain for 13 out of 22 objects with M SpT results that are compatible within one subclass with the correct SpT (see Table 4). The differences can be due to the imperfect telluric removal in the first interval of interest of this index.…”

Section: Appendix A: Comments On Individual Objectssupporting

confidence: 84%

X-shooter spectroscopy of young stellar objects

Manara

Testi

Rigliaco

et al. 2013

A&A

149

265

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Context. The lack of knowledge of photospheric parameters and the level of chromospheric activity in young low-mass pre-main sequence stars introduces uncertainties when measuring mass accretion rates in accreting (Class II) young stellar objects. A detailed investigation of the effect of chromospheric emission on the estimates of mass accretion rate in young low-mass stars is still missing. This can be undertaken using samples of young diskless (Class III) K and M-type stars. Aims. Our goal is to measure the chromospheric activity of Class III pre main sequence stars to determine its effect on the estimates of the accretion luminosity (L acc ) and mass accretion rate (Ṁ acc ) in young stellar objects with disks. Methods. Using VLT/X-shooter spectra, we analyzed a sample of 24 nonaccreting young stellar objects of spectral type between K5 and M9.5. We identified the main emission lines normally used as tracers of accretion in Class II objects, and we determined their fluxes in order to estimate the contribution of the chromospheric activity to the line luminosity. Results. We have used the relationships between line luminosity and accretion luminosity derived in the literature for Class II objects to evaluate the impact of chromospheric activity on the accretion rate measurements. We find that the typical chromospheric activity would bias the derived accretion luminosity by L acc,noise < 10 −3 L , with a strong dependence on the T eff of the objects. The noise oṅ M acc depends on stellar mass and age, and the typical values of log(Ṁ acc,noise ) range between ∼−9.2 to −11.6 M /yr. Conclusions. Values of L acc 10 −3 L obtained in accreting low-mass pre main sequence stars through line luminosity should be treated with caution because the line emission may be dominated by the contribution of chromospheric activity.

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Section: Appendix A: Comments On Individual Objectssupporting

confidence: 84%

X-shooter spectroscopy of young stellar objects

Manara

Testi

Rigliaco

et al. 2013

A&A

149

265

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“…Disks around VLMSs and BDs are observed to be more frequent than around higher-mass stars in σ Orionis (Luhman et al 2008b;Peña Ramírez et al 2012), λ Orionis (Bayo et al 2012), the Upper Scorpius association (Luhman & Mamajek 2012;Lodieu 2013) and the nearby young cluster NGC 1333 (Scholz et al 2012). The opposite trend is seen in Chamaeleon I (Luhman et al 2008a(Luhman et al , 2010.…”

Section: Molecular Outflows Accretion Disks and Disk Frequencies Aromentioning

confidence: 90%

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Marks¹,

Martín

Béjar

et al. 2017

A&A

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Context. Whether brown dwarfs (BDs) form just as stars directly from the gravitational collapse of a molecular cloud core ("star-like") or whether BDs and some very low-mass stars (VLMSs) constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk ("peripheral") fragmentation, is one of the key questions of the star-formation problem. Aims. For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above ≈ 0.2M⊙, while for BDs it is < 10%. Here we investigate a case in which BDs in Taurus formed dominantly, but not exclusively, through peripheral fragmentation, which naturally results in low binary fractions. The decline of the binary frequency in the transition region between star-like formation and peripheral formation is modelled. Methods. A dynamical population synthesis model is employed in which stellar binary formation is universal with a large binary fraction close to unity. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), own orbital parameter distributions for binaries and a low binary fraction according to observations and expectations from smoothed particle hydrodynamics (SPH) and grid-based computations. A small amount of dynamical processing of the stellar component is accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. Results. The binary fraction declines strongly in the transition region between star-like and peripheral formation, exhibiting characteristic features. The location of these features and the steepness of this trend depend on the masslimits for star-like and peripheral formation. Such a trend might be unique to low density regions like Taurus which host dynamically largely unprocessed binary populations in which the binary fraction is large for stars down to M-dwarfs and low for BDs. Conclusions. The existence of a strong decline in the binary fraction -primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is a test of the (non-)continuity of star formation along the mass-scale, the separateness of the stellar and BD populations and the dominant formation channel for BDs and BD binaries in regions of low stellar density hosting dynamically unprocessed populations.

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“…Observationally, several young star forming regions have been probed to faint magnitudes at both optical and near-infrared wavelengths to look for a possible cut-off at the low-mass end of the mass function and the results significantly vary from region to region. A possible cutoff below ∼6 M J up to 20 M J have been reported in NGC 1333 (e.g., Scholz et al 2009Scholz et al , 2012. Moreover, there is no universal agreement on the behavior of the mass function over this cut-off.…”

Section: Introductionmentioning

confidence: 94%

Searching for planetary-mass T-dwarfs in the core of Serpens

Spezzi

Oliveira

Moraux

et al. 2012

A&A

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Context. The knowledge of the present-day mass function of young clusters and the mass of their coolest substellar members is essential to clarify the brown dwarf formation mechanism, which still remains a matter of debate. Aims. We searched for isolated planetary-mass T-dwarfs in the ∼3 Myr old Serpens Core cluster. Methods. We performed a deep imaging survey of the central part of this cluster using the WIRCam camera at the CFHT. Observations were performed through the narrow-band CH 4 off and CH 4 on filters, to identify young T-dwarfs from their 1.6 μm methane absorption bands, and the broad-band JHK S filters, to better characterize the selected candidates. We complemented our WIRCam photometry with optical imaging data from MegaCam at CFHT and Suprime-Cam at the Subaru telescope and mid-infrared flux measurements from the Spitzer "core to disk" (c2d) Legacy Survey. Results. We report four faint T-dwarf candidates in the direction of the Serpens Core with CH 4 on−CH 4 off above 0.2 mag, estimated visual extinction in the range 1−9 mag and spectral type in the range T1−T5 based on their dereddened CH 4 on−CH 4 off colors. Comparisons with T-dwarf spectral models and optical to mid-infrared color-color and color-magnitude diagrams, indicate that two of our candidates (ID 1 and 2) are background contaminants (most likely heavily reddened low-redshift quasars). The properties of the other two candidates (ID 3 and 4) are consistent with them being young members of the Serpens Core cluster, although our analysis can not be considered conclusive. In particular, ID 3 may also be a foreground T-dwarf. It is detected by the Spitzer c2d survey but only flux upper limits are available above 5.8 μm and, hence, we can not assess the presence of a possible disk around this object. However, it presents some similarities with other young T-dwarf candidates (S Ori 70 in the σ Orionis cluster and CFHT_J0344+3206 in the direction of IC 348). If ID 3 and 4 belong to Serpens, they would have a mass of a few Jupiter masses and would be amongst the youngest, lowest mass objects detected in a star-forming region so far.

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Substellar Objects in Nearby Young Clusters (Sonyc). Iv. A Census of Very Low Mass Objects in NGC 1333

Cited by 85 publications

References 65 publications

X-shooter spectroscopy of young stellar objects

X-shooter spectroscopy of young stellar objects

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Searching for planetary-mass T-dwarfs in the core of Serpens

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