The Lower Mass Function of Young Open Clusters

Bouvier, J.; Moraux, E.; Stauffer, J. R.; Barrado, D.; Cuillandre, J. C.

doi:10.1017/s0074180900210474

Cited by 6 publications

(3 citation statements)

References 12 publications

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“…We note that a power law relation with a slope of −0.6 is approximately the slope of the mass function for masses between 0.4 and ∼0.1 M found in other young open clusters (see e.g. Bouvier et al 2003). We thus conclude that down to ∼0.1 M , IC 4665 confirms this trend of the mass function.…”

Section: The Mass Functionsupporting

confidence: 79%

“…However, it is only for a handful regions that the mass distribution has been derived crossing the sub-stellar boundary at 0.072 M , (see Bouvier et al 2003, and references therein). The mass function of young open clusters with an age of ∼100 Myr seems best described by a lognormal law over the full mass range in a dN/dlog M presentation, regardless of their exact age, metallicity or richness.…”

Section: Introductionmentioning

confidence: 99%

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Exploring the lower mass function in the young open cluster IC 4665

Wit¹,

Bouvier²,

Palla

et al. 2006

A&A

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We present a study of the young (30−100 Myr) open cluster IC 4665 with the aim to determine the shape of the mass function well into the brown dwarf regime. We photometrically select 691 low-mass stellar and 94 brown dwarf candidate members over an area of 3.82 square degrees centred on the cluster. K-band follow-up photometry and Two-Micron All-Sky Survey data allow a first filtering of contaminant objects from our catalogues. A second filtering is performed for the brightest stars using proper motion data provided by the Tycho-2 and UCAC2 public catalogues. Contamination by the field population for the lowest mass objects is estimated using same latitude control fields. We fit observed surface densities of various cluster populations with King profiles and find a consistent tidal radius of 1.0• . The presence of possible mass segregation is discussed. In most respects investigated, IC 4665 is similar to other young open clusters at this age: (1) a power law fit to the mass function between 1 and 0.04 M results in best fit for a slope of −0.6; (2) a cusp in the mass function is noticed at about the substellar boundary with respect to the power law description, the interpretation of which is discussed; (3) a fraction between 10−19% for BDs with M > ∼ 0.03 M to total members; (4) a best-fit lognormal function to the full mass distribution shows an average member mass of 0.32 M , if IC 4665 has an age of 50 Myr.

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Section: The Mass Functionsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Exploring the lower mass function in the young open cluster IC 4665

Wit¹,

Bouvier²,

Palla

et al. 2006

A&A

View full text Add to dashboard Cite

show abstract

“…Measurements of the brown dwarf mass function in a variety of moderate-age clusters (>100 Myr) are finding results in the range / m À0.5 to / m À0.6 (Bouvier et al 2003), suggesting a mass function that is continuous with the stellar function but continues to turn over at lower and lower masses, extending into the T dwarf range in some clusters.…”

Section: Cluster T Dwarfsmentioning

confidence: 99%

The 2MASS Wide-Field T Dwarf Search. IV. Hunting Out T Dwarfs with Methane Imaging

et al. 2005

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We present first results from a major program of methane filter photometry for low-mass stars and brown dwarfs. The definition of a new methane filter photometric system is described. A recipe is provided for the differential calibration of methane imaging data using existing Two Micron All Sky Survey (2MASS) photometry. We show that these filters are effective in discriminating T dwarfs from other types of stars, and we demonstrate this with AngloAustralian Telescope observations using the IRIS2 imager. Methane imaging data and proper motions are presented for 10 T dwarfs identified as part of the 2MASS Wide-Field T Dwarf Search, seven of them initially identified as T dwarfs using methane imaging. We also present near-infrared moderate-resolution spectra for five T dwarfs newly discovered by this technique. Spectral types obtained from these spectra are compared to those derived from both our methane filter observations and spectral types derived by other observers. Finally, we suggest a range of future programs to which these filters are clearly well suited: the winnowing of T dwarf and Y dwarf candidate objects coming from the next generation of near-infrared sky surveys, the robust detection of candidate planetary-mass brown dwarfs in clusters, the detection of T dwarf companions to known L and T dwarfs via deep methane imaging, and the search for rotationally modulated time-variable surface features on cool brown dwarfs.

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The Stellar and Sub-Stellar Initial Mass Function of Simple and Composite Populations

Kroupa

Weidner

Pflamm-Altenburg

et al. 2013

Planets, Stars and Stellar Systems

385

491

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The distribution of stellar masses that form together, the initial mass function (IMF), is one of the most important astrophysical distribution functions. The determination of the IMF is a very difficult problem because stellar masses cannot be measured directly and because observations usually cannot assess all stars in a population requiring elaborate bias corrections. Nevertheless, impressive advances have been achieved during the last decade, such that the shape of the IMF is reasonably well understood from low-mass brown dwarfs (BDs) to very massive stars. The case can be made for a rather universal form that can be well approximated by a two-part power-law function in the stellar regime. However, there exists a possible hint for a systematic variation with metallicity. From very elaborate observational surveys a picture is emerging according to which the binary properties of very-low-mass stars (VLMSs) and BDs may be fundamentally different from those of late-type stars implying the probable existence of a discontinuity in the IMF, but the surveys also appear to suggest the number of BDs per star to be independent of the physical conditions of current Galactic star formation. Star-burst clusters and thus globular cluster may, however, have a much larger abundance of BDs. Very recent advances have allowed the measurement of the physical upper stellar mass limit, which also appears to be disconcertingly robust to variations in metallicity. Furthermore, it now appears that star clusters are formed in a rather organised fashion from lowto high stellar masses, such that the most-massive stars just forming terminate further star-formation within the particular cluster. Populations formed from many star clusters, composite populations, would then have steeper IMFs (fewer massive stars per low-mass star) than the simple populations in the constituent clusters. A near invariant star-cluster mass function implies the maximal cluster mass to correlate with the galaxy-wide star-formation rate. This then leads to the result that the composite-stellar IMFs vary in dependence of galaxy type, with potentially dramatic implications for theories of galaxy formation and evolution.The simple and composite IMF 5 30 Dor cluster (R136) in the LMC, NGC 3603 in the MW, and the Arches cluster near the Galactic centre. The 30 Dor star-burst cluster (

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The Lower Mass Function of Young Open Clusters

Cited by 6 publications

References 12 publications

Exploring the lower mass function in the young open cluster IC 4665

Exploring the lower mass function in the young open cluster IC 4665

The 2MASS Wide-Field T Dwarf Search. IV. Hunting Out T Dwarfs with Methane Imaging

The Stellar and Sub-Stellar Initial Mass Function of Simple and Composite Populations

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