Structure and Mass Function of Open Cluster NGC 6910

NGC 6910 is located in a Cygnus X region, which is a ∼10◦ complex of actively star forming molecular clouds and young clusters, located at a distance of about 1.7 kpc (Reipurth & Schneider 2008). Open clusters possess many favorable characteristics for initial mass function (IMF) studies. The observed mass function of a star cluster can in principle be determined from the observed luminosity function (LF) using theoretical stellar evolutionary models. Here, we are presenting our initial results related to structure parameters, extinction, distance and mass function of open cluster NGC 6910 based on the deep and wide field mosaic images taken from 1.0m Sampurnand telescope of ARIES, India.

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Luminosity Function of Some Open Clusters

ISRN Astronomy and Astrophysics ◽

10.5402/2011/127030 ◽

2011 ◽

Vol 2011 ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

W. H. Elsanhoury ◽

M. A. Hamdy ◽

M. I. Nouh ◽

A. S. Saad ◽

S. M. Saad

Keyword(s):

Luminosity Function ◽

Mass Function ◽

Statistical Investigation ◽

Open Clusters ◽

Initial Mass Function ◽

Initial Mass ◽

Classical Definition ◽

Different Ages ◽

The Imf

We investigated the luminosity function (LF) and initial mass function (IMF) of some open clusters having different ages. To calculate the LF, we followed the classical definition by van Rhijn (1936). Statistical investigation of the dispersion around a range of magnitudes concerning what is called Wielen dip revealed that the dip is unreal. To confirm the unreality of the dip, we computed the IMF for these open clusters, the statistical investigation of the IMF confirmed the results obtained using the LF, that is, there is no dip for these open clusters under study.

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The Variation of the Initial Mass Function in Clusters

Symposium - International Astronomical Union ◽

10.1017/s0074180900241648 ◽

2004 ◽

Vol 221 ◽

pp. 237-246

Author(s):

K. L. Luhman

Keyword(s):

Star Formation ◽

Brown Dwarfs ◽

Mass Function ◽

Open Clusters ◽

Initial Mass Function ◽

Initial Mass ◽

Star Forming ◽

Star Forming Regions

I review recent measurements of the initial mass function of stars and brown dwarfs in star-forming regions and open clusters and summarize the implications of these data for theories of star formation.

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The Dynamical Evolution of Young Open Clusters

Symposium - International Astronomical Union ◽

10.1017/s0074180900147680 ◽

1985 ◽

Vol 113 ◽

pp. 463-465

Author(s):

Michael Margulis ◽

Charles J. Lada ◽

David Dearborn

Keyword(s):

Potential Function ◽

Molecular Clouds ◽

Initial Conditions ◽

Stellar System ◽

Dynamical Evolution ◽

Mass Function ◽

Open Clusters ◽

Stellar Systems ◽

Spherically Symmetric ◽

Star Forming

Using numerical N-body calculations we have simulated the dynamical evolution of young clusters as they emerge from molecular clouds. Starting with initially virialized systems of stars and gas we follow the evolution of these systems from the time immediately after the stars have formed in a cloud until a time long after all the residual star-forming gas has been dispersed. In the models stellar systems were composed of 50, and in some cases 100, stars and these stars were represented as point masses. The stellar mass function followed a power law with an index of −2.5 and ranged over two decades in mass (Scalo 1978). Gas in the models was represented as an extra term in the gravitational potential function governing stellar motions, and was set to follow a density distribution corresponding to a spherically symmetric Plummer potential function (Plummer 1911). Starting with these initial conditions, stellar motions were then integrated and evolution of each stellar system was followed as gas was dispersed from the vicinity of the stars as a function of time.

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Lupus DANCe

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038717 ◽

2020 ◽

Vol 643 ◽

pp. A148

Author(s):

P. A. B. Galli ◽

H. Bouy ◽

J. Olivares ◽

N. Miret-Roig ◽

R. G. Vieira ◽

...

Keyword(s):

Molecular Clouds ◽

3D Structure ◽

Mass Range ◽

Mass Function ◽

Space Mission ◽

Initial Mass Function ◽

Young Stars ◽

Star Forming ◽

Star Forming Regions ◽

Kinematic Properties

Context. Lupus is recognised as one of the closest star-forming regions, but the lack of trigonometric parallaxes in the pre-Gaia era hampered many studies on the kinematic properties of this region and led to incomplete censuses of its stellar population. Aims. We use the second data release of the Gaia space mission combined with published ancillary radial velocity data to revise the census of stars and investigate the 6D structure of the Lupus complex. Methods. We performed a new membership analysis of the Lupus association based on astrometric and photometric data over a field of 160 deg2 around the main molecular clouds of the complex and compared the properties of the various subgroups in this region. Results. We identified 137 high-probability members of the Lupus association of young stars, including 47 stars that had never been reported as members before. Many of the historically known stars associated with the Lupus region identified in previous studies are more likely to be field stars or members of the adjacent Scorpius-Centaurus association. Our new sample of members covers the magnitude and mass range from G ≃ 8 to G ≃ 18 mag and from 0.03 to 2.4 M⊙, respectively. We compared the kinematic properties of the stars projected towards the molecular clouds Lupus 1–6 and showed that these subgroups are located at roughly the same distance (about 160 pc) and move with the same spatial velocity. Our age estimates inferred from stellar models show that the Lupus subgroups are coeval (with median ages ranging from about 1 to 3 Myr). The Lupus association appears to be younger than the population of young stars in the Corona-Australis star-forming region recently investigated by our team using a similar methodology. The initial mass function of the Lupus association inferred from the distribution of spectral types shows little variation compared to other star-forming regions. Conclusions. In this paper, we provide an updated sample of cluster members based on Gaia data and construct the most complete picture of the 3D structure and 3D space motion of the Lupus complex.

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The role of molecular filaments in the origin of the prestellar core mass function and stellar initial mass function

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935915 ◽

2019 ◽

Vol 629 ◽

pp. L4 ◽

Cited By ~ 13

Author(s):

Ph. André ◽

D. Arzoumanian ◽

V. Könyves ◽

Y. Shimajiri ◽

P. Palmeirim

Keyword(s):

Power Law ◽

Molecular Clouds ◽

Mass Function ◽

Initial Mass Function ◽

Initial Mass ◽

Core Mass ◽

Filamentary Structure ◽

Star Forming ◽

Prestellar Cores ◽

Stellar Initial Mass Function

Context. The origin of the stellar initial mass function (IMF) is one of the most debated issues in astrophysics. Aims. Here we explore the possible link between the quasi-universal filamentary structure of star-forming molecular clouds and the origin of the IMF. Methods. Based on our recent comprehensive study of filament properties from Herschel Gould Belt survey observations, we derive, for the first time, a good estimate of the filament mass function (FMF) and filament line mass function (FLMF) in nearby molecular clouds. We use the observed FLMF to propose a simple toy model for the origin of the prestellar core mass function (CMF), relying on gravitational fragmentation of thermally supercritical but virialized filaments. Results. We find that the FMF and the FLMF have very similar shapes and are both consistent with a Salpeter-like power-law function (dN/dlog Mline ∝ Mline−1.5±0.1) in the regime of thermally supercritical filaments (Mline > 16 M⊙ pc−1). This is a remarkable result since, in contrast, the mass distribution of molecular clouds and clumps is known to be significantly shallower than the Salpeter power-law IMF, with dN/dlog Mcl ∝ Mcl−0.7. Conclusions. Since the vast majority of prestellar cores appear to form in thermally transcritical or supercritical filaments, we suggest that the prestellar CMF and by extension the stellar IMF are at least partly inherited from the FLMF through gravitational fragmentation of individual filaments.

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The Brown Dwarf Deficit in Taurus: Evidence for a Non-Universal IMF

Symposium - International Astronomical Union ◽

10.1017/s0074180900210322 ◽

2003 ◽

Vol 211 ◽

pp. 81-82 ◽

Cited By ~ 2

Author(s):

César Briceño ◽

Kevin L. Luhman ◽

Lee Hartmann ◽

John R. Stauffer ◽

J. Davy Kirkpatrick

Keyword(s):

Brown Dwarfs ◽

Mass Function ◽

Initial Mass Function ◽

Wide Field ◽

Low Density ◽

Brown Dwarf ◽

New Members ◽

Star Forming ◽

Field Imaging ◽

Wide Field Imaging

We present the results of a deep, optical/IR wide field imaging survey of selected fields in the nearby (d~ 140 pc) Taurus star-forming region. We report the discovery of 9 new members with spectral types M5.75–M9.5. We derive an Initial Mass Function encompassing 54% of the known members in Taurus. Comparison with dense regions like the Trapezium Cluster in Orion shows that Taurus has produced x2 less brown dwarfs. We suggest that the lower frequency of brown dwarfs in Taurus may result from the low-density star-forming environment, leading to larger minimum Jeans masses.

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Very Low-Luminosity Objects in Star-Forming Regions

Highlights of Astronomy ◽

10.1017/s1539299600021626 ◽

1998 ◽

Vol 11 (1) ◽

pp. 423-424

Author(s):

Motohide Tamura ◽

Yoichi Itoh ◽

Yumiko Oasa ◽

Alan Tokunaga ◽

Koji Sugitani

Keyword(s):

Brown Dwarfs ◽

Mass Function ◽

T Tauri Stars ◽

Initial Mass Function ◽

Formation Mechanisms ◽

Star Forming ◽

Star Forming Regions ◽

T Tauri ◽

Low Mass ◽

Stellar Sources

Abstract In order to tackle the problems of low-mass end of the initial mass function (IMF) in star-forming regions and the formation mechanisms of brown dwarfs, we have conducted deep infrared surveys of nearby molecular clouds. We have found a significant population of very low-luminosity sources with IR excesses in the Taurus cloud and the Chamaeleon cloud core regions whose extinction corrected J magnitudes are 3 to 8 mag fainter than those of typical T Tauri stars in the same cloud. Some of them are associated with even fainter companions. Follow-up IR spectroscopy has confirmed for the selected sources that their photospheric temperature is around 2000 to 3000 K. Thus, these very low-luminosity young stellar sources are most likely very low-mass T Tauri stars, and some of them might even be young brown dwarfs.

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