The Initial Mass Function in the Taurus Star‐forming Region

Briceño, César; Luhman, K. L.; Hartmann, L.; Stauffer, J. R.; Kirkpatrick, J. Davy

doi:10.1086/343127

Cited by 327 publications

(637 citation statements)

References 75 publications

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“…The N-body models of Kroupa & Bouvier (2003b) show that Taurus-Auriga like arrangements are largely unevolved and in particular that the binary properties should be similar to those at birth, with some dynamical evolution . 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).…”

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

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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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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

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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%

“…For targets with more than one photometric measurement, the median value was adopted. Uncertainties were not reported in up to half of the the literature sources, therefore, to account for both source variability and the uncertainties in the photometric transformation to the Cousins system, adopted common values for the R C and I C uncertainties were used (e.g., Briceño et al 2002;Mayne et al 2012). The error adopted for R C was 0.8 mag, and the error adopted for I C was 0.3 mag.…”

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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“…We briefly review some of the typical clusters subject to investigation: IC 348 (Preibisch et al 2003;Muench et al 2003;Luhman et al 2003), Taurus (Luhman 2000;Briceño et al 2002), Orion trapezium (Hillenbrand & Carpenter 2000;Luhman et al 2000;Muench et al 2002), Pleiades (Bouvier et al 1998;Luhman et al 2000), and M35 (Barrado y Navascués et al 2001). …”

Section: The Masses In Open Clustersmentioning

confidence: 99%

The Initial Mass Function as given by the fragmentation

Zaninetti¹

2005

Astron. Nachr.

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Abstract.The dichotomy between a universal mass function (IMF) and a variable IMF which depends on local physical parameters characterises observational and theoretical stellar astronomy. In this contribution the available distributions of probability are briefly reviewed. The physical nature of two of them, gamma variate and lognormal, is then explained once the framework of the fragmentation is introduced. Interpolating techniques are then applied to the sample of the first 10 pc and to the open cluster NGC 6649: in both cases lognormal distribution produces the best fit. The three power law function has also been investigated and visual comparison with an artificially generated sample of 100000 stars suggests that the variations in the spectral index are simply due to the small number of stars available in the observational sample. In order to derive the sample of masses, a new formula that allows us to express the mass as a function of the absolute magnitude and (B-V) for MAIN V, GIANTS III and SUPERGIANTS I is derived.

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The Initial Mass Function in the Taurus Star‐forming Region

Cited by 327 publications

References 75 publications

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

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

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey

The Initial Mass Function as given by the fragmentation

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