New Low‐Mass Members of the Taurus Star‐forming Region

Luhman, K. L.; Briceño, César; Stauffer, J. R.; Hartmann, L.; Barrado, D.; Caldwell, Nelson

doi:10.1086/374983

Cited by 167 publications

(234 citation statements)

References 28 publications

(92 reference statements)

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“…Our simulation volume is large enough to contain Taurus-like structures. The velocity dispersion at the earlier time shown from our simulation is the closest to what is seen in Taurus, consistent with the view that the Taurus area is still relatively young (e.g., Hartmann et al 2001;Luhman et al 2003Luhman et al , 2007Pineda et al 2010).…”

Section: Analysis Of the Profilessupporting

confidence: 87%

Molecular cloud formation as seen in synthetic H i and molecular gas observations

Heiner¹,

Vázquez‐Semadeni²,

Ballesteros-Paredes³

2015

Mon. Not. R. Astron. Soc.

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We present synthetic Hi and CO observations of a numerical simulation of decaying turbulence in the thermally bistable neutral medium. We first present the simulation, which produces a clumpy medium, with clouds initially consisting of clustered clumps. Self-gravity causes these clump clusters to merge and form more homogeneous dense clouds. We apply a simple radiative transfer algorithm, throwing rays in many directions from each cell, and defining every cell with A v > 1 as molecular. We then produce maps of Hi, CO-free molecular gas, and CO, and investigate the following aspects: i) The spatial distribution of the warm, cold, and molecular gas, finding the well-known layered structure, with molecular gas being surrounded by cold Hi and this in turn being surrounded by warm Hi. ii) The velocity of the various components, finding that the atomic gas is generally flowing towards the molecular gas, and that this motion is reflected in the frequently observed bimodal shape of the Hi profiles. This conclusion is, however, tentative, because we do not include feedback that may produce Hi gas receding from molecular regions. iii) The production of Hi self-absorption (HISA) profiles, and the correlation of HISA with molecular gas. In particular, we test the suggestion of using the second derivative of the brightness temperature Hi profile to trace HISA and molecular gas, finding significant limitations. On a scale of several parsecs, some agreement is obtained between this technique and actual HISA, as well as a correlation between HISA and the molecular gas column density. This correlation, however, quickly deteriorates towards sub-parsec scales. iv) The column density PDFs of the actual Hi gas and those recovered from the Hi line profiles, finding that the latter have a cutoff at column densities where the gas becomes optically thick, thus missing the contribution from the HISA-producing gas. We also find that the powerlaw tail typical of gravitational contraction is only observed in the molecular gas, and that, before the power-law tail develops in the total gas density PDF, no CO is yet present, reinforcing the notion that gravitational contraction is needed to produce this component.

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Section: Analysis Of the Profilessupporting

confidence: 87%

Molecular cloud formation as seen in synthetic H i and molecular gas observations

Heiner¹,

Vázquez‐Semadeni²,

Ballesteros-Paredes³

2015

Mon. Not. R. Astron. Soc.

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“…Hence, in order to retain the important I-band magnitude for further analysis, we prefer to adopt A v given by the J − H and H − K s colours, throughout the remainder of this paper. We note here also, that in addition, we performed similar experiments using a locus in the I − K s , J − H diagram, as adopted by Luhman et al (2003) for a study of the Taurus SFR, and found very similar values of A v in excellent agreement with our preferred methods. Lastly, we are aware that dereddening to dwarf loci may not be correct for NGC 2264 at age 3 Myr, since young objects have surface gravities intermediate between dwarfs and giants (Greene & Lada 1996).…”

Section: Dereddening the Samplesupporting

confidence: 77%

A deep, wide-field search for substellar members in NGC 2264

Kendall

Bouvier

Moraux³

et al. 2005

A&A

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Abstract.We report the first results of our ongoing campaign to discover the first brown dwarfs (BD) in NGC 2264, a young (3 Myr), populous star forming region for which our optical studies have revealed a very high density of potential candidates -236 in <1 deg 2 -from the substellar limit down to at least ∼20 M Jup for zero reddening. Candidate BD were first selected using wide field (I, z) band imaging with CFH12K, by reference to current theoretical isochrones. Subsequently, 79 (33%) of the I, z sample were found to have near-infrared 2MASS photometry (JHK s ± 0.3 mag or better), yielding dereddened magnitudes and allowing further investigation by comparison with the location of NextGen and DUSTY isochrones in colourcolour and colour-magnitude diagrams involving various combinations of I, J, H and K s . We discuss the status and potential substellarity of a number of relatively unreddened (A v < ∼ 5) likely low-mass members in our sample, but in spite of the depth of our observations in I, z, we are as yet unable to unambiguously identify substellar candidates using only 2MASS data. Nevertheless, there are excellent arguments for considering two faint (observed I ∼ 18.4 and 21.2) objects as cluster candidates with masses respectively at or rather below the hydrogen burning limit. More current candidates could be proven to be cluster members with masses around 0.1 M via gravity-sensitive spectroscopy, and deeper near-infrared imaging will surely reveal a hitherto unknown population of young brown dwarfs in this region, accessible to the next generation of deep near-infrared surveys.

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“…The original measurements were in the R C and I C filters for those targets reported in Kenyon & Hartmann (1995), whilst all other compiled literature studies transformed the measured photometric value into the Cousins system (Guieu et al 2007(Guieu et al , 2006Luhman 2000Luhman , 2004Luhman et al 2003a;Briceño et al 1999Briceño et al , 2002Martín et al 2001). For targets with more than one photometric measurement, the median value was adopted.…”

Section: Construction Of Spectral Energy Distributionsmentioning

confidence: 99%

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey

Bulger

Patience

Ward-Duong

et al. 2014

A&A

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With the PACS instrument on Herschel, 134 low mass members of the Taurus star-forming region spanning the M4-L0 spectral type range and covering the transition from low mass stars to brown dwarfs were observed. Combining the new Herschel results with other Herschel programs, a total of 150 of the 154 M4-L0 Taurus members have observations, and we have added an additional 3 targets from Spitzer to form the 153-object TBOSS (Taurus Boundary of Stellar/Substellar) sample, a 99% complete study. Among the 150 targets, 70 µm flux densities were measured for 7 of the 7 Class I objects, 48 of the 67 Class II objects, and 3 of the 76 Class III objects. For the detected Class II objects, the median 70 µm flux density level declines with spectral type; however, the distribution of excess relative to central object flux density does not change across the stellar/substellar boundary in the M4-L0 range. Connecting the 70 µm TBOSS values with the results from K0-M3 Class II members results in the first comprehensive census of far-IR emission across the full mass spectrum of the stellar and substellar population of a star-forming region, and the median flux density declines with spectral type in a trend analogous to the flux density decline expected for the central objects. Spectral energy distributions (SEDs) were constructed for all TBOSS targets covering the optical to far-IR range and extending to the submm/mm for a subset of sources with longer wavelength data. Based on an initial exploration of the impact of different physical parameters on the Herschel flux densities, geometrical factors such as inclination and structural parameters such as scale height and flaring have the largest influence on the flux densities in the PACS bands. From the 24 µm to 70 µm spectral index of the SEDs, 5 new candidate transition disks were identified. Considering the previously known and new candidate transition disks, the spectral indices over longer wavelengths (≥70 µm) are not distinct from those of the full Class II population, suggesting that the outer regions of the transition disks are similar to Class II disks. The steep 24 µm to 70 µm slope for a subset of 8 TBOSS targets may be an indication of truncated disks in these systems, however additional measurements are required to establish the outer radii of these disks conclusively. From existing high angular resolution companion search observations, two examples of mixed pair systems that include secondaries with disks were measured in the Herschel data. Finally, comparing the TBOSS results with a Herschel study of Ophiuchus brown dwarfs reveals a lower fraction of disks around the Taurus substellar population with flux densities comparable to the Ophiuchus disks.

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New Low‐Mass Members of the Taurus Star‐forming Region

Cited by 167 publications

References 28 publications

Molecular cloud formation as seen in synthetic H i and molecular gas observations

Molecular cloud formation as seen in synthetic H i and molecular gas observations

A deep, wide-field search for substellar members in NGC 2264

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey

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