Seventeen new very low-mass members in Taurus

Guieu, S.; Dougados, C.; Monin, Jean‐Louis; Magnier, E. A.; Martín, E. L.

doi:10.1051/0004-6361:20053493

Cited by 100 publications

(166 citation statements)

References 56 publications

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“…At a distance of 140pc (Guieu et al 2006), with mK between 13.7 and 14.9, for 1 Myr old objects the Lyon DUSTY model isochrones predict 0.02M < M < 0.03M and 3.72 < log g < 3.79 for KPNO-Tau 1 and KPNO-Tau 4, and 0.006M < M < 0.007M and 3.50 < log g < 3.51 for KPNO-Tau 12. At a distance of 435pc (Stassun, Mathieu, & Valenti 2006), with mK = 13.8, the Lyon DUSTY model isochrones predict a total mass M = 0.07M and log g = 3.54 for 2MASS 0535−0546.…”

Section: The 1-2 Myr Objectsmentioning

confidence: 92%

Towards precise ages and masses of Free Floating Planetary Mass Brown Dwarfs

Canty¹,

Lucas²,

Roche³

et al. 2013

Monthly Notices of the Royal Astronomical Society

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Measurement of the substellar initial mass function (IMF) in very young clusters is hampered by the possibility of the age spread of cluster members. This is particularly serious for candidate planetary mass objects (PMOs), which have a very similar location to older and more massive brown dwarfs on the Hertzsprung-Russell Diagram (HRD). This degeneracy can be lifted by the measurement of gravity sensitive spectral features. To this end we have obtained medium resolution (R≈5000) Near-infrared Integral Field Spectrometer (NIFS) K band spectra of a sample of late M-/early L-type dwarfs. The sample comprises old field dwarfs and very young brown dwarfs in the Taurus association and in the σ Orionis cluster. We demonstrate a positive correlation between the strengths of the 2.21 µm NaI doublet and the objects' ages. We demonstrate a further correlation between these objects' ages and the shape of their K band spectra. We have quantified this correlation in the form of a new index, the H 2 (K) index. This index appears to be more gravity-sensitive than the NaI doublet and has the advantage that it can be computed for spectra where gravity-sensitive spectral lines are unresolved, while it is also more sensitive to surface gravity at very young ages (<10 Myr) than the triangular H band peak. Both correlations differentiate young objects from field dwarfs, while the H 2 (K) index can distinguish, at least statistically, populations of ∼1 Myr objects from populations of ∼10 Myr objects. We applied the H 2 (K) index to NIFS data for one Orion nebula cluster (ONC) PMO and to previously published low resolution spectra for several other ONC PMOs where the 2.21 µm NaI doublet was unresolved and concluded that the average age of the PMOs is ∼1 Myr.

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Section: The 1-2 Myr Objectsmentioning

confidence: 92%

Towards precise ages and masses of Free Floating Planetary Mass Brown Dwarfs

Canty¹,

Lucas²,

Roche³

et al. 2013

Monthly Notices of the Royal Astronomical Society

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“…since been discovered (Luhman 2004b;Guieu et al 2006). and Thies & Kroupa (2008) show that there is no need to invoke a non-canonical IMF in Taurus.…”

Section: Taurusmentioning

confidence: 99%

Inverse dynamical population synthesis

Marks

Kroupa

2012

A&A

246

302

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Binary populations in young star clusters show multiplicity fractions both lower and up to twice as high as those observed in the Galactic field. We follow the evolution of a population of binary stars in dense and loose star clusters starting with an invariant initial binary population and a formal multiplicity fraction of unity, and demonstrate that these models can explain the observed binary properties in Taurus, ρ Ophiuchus, Chamaeleon, Orion, IC 348, Upper Scorpius A, Praesepe, and the Pleiades. The model needs to consider solely different birth densities for these regions. The evolved theoretical orbital-parameter distributions are highly probable parent distributions for the observed ones. We constrain the birth conditions (stellar mass, M ecl , and half-mass radius, r h ) for the derived progenitors of the star clusters and the overall present-day binary fractions allowed by the present model. The results compare very well with properties of molecular cloud clumps on the verge of star formation. Combining these with previously and independently obtained constraints on the birth densities of globular clusters, we identify a weak stellar mass -half-mass radius correlation for cluster-forming cloud clumps, r h /pc ∝ (M ecl /M ) 0.13 ± 0.04 . The ability of the model to reproduce the binary properties in all the investigated young objects, covering present-day densities from 1−10 stars pc −3 (Taurus) to 2 × 10 4 stars pc −3 (Orion), suggests that environment-dependent dynamical evolution plays an important role in shaping the present-day properties of binary populations in star clusters, and that the initial binary properties may not vary dramatically between different environments.

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“…Taurus exhibits a paucity of high-mass young stars (Kenyon et al 2008) and was originally proposed to be deficient in low-mass stars (Briceño et al 2002) as well. Many brown dwarfs have however since been discovered (Luhman 2004;Guieu et al 2006). Kroupa et al (2003) and Thies & Kroupa (2008) show that there is no need to invoke a non-canonical IMF in Taurus.…”

Section: The Stellar and Substellar Population Inmentioning

confidence: 99%

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

Marks¹,

Martín

Béjar

et al. 2017

A&A

Self Cite

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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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Seventeen new very low-mass members in Taurus

Cited by 100 publications

References 56 publications

Towards precise ages and masses of Free Floating Planetary Mass Brown Dwarfs

Towards precise ages and masses of Free Floating Planetary Mass Brown Dwarfs

Inverse dynamical population synthesis

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

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