scholarly journals Luminosity Function of Some Open Clusters

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
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.

scholarly journals The Initial Mass Function of Young Open Clusters in the Galaxy: A Preliminary Result

2015 ◽  
Vol 12 (S316) ◽  
pp. 357-358
Author(s):  
Beomdu Lim ◽  
Hwankyung Sung ◽  
Hyeonoh Hur ◽  
Byeong-Gon Park
Keyword(s):  
Star Formation ◽  
Environmental Conditions ◽  
Mass Function ◽  
Open Clusters ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Formation Processes ◽  
Global Properties ◽  
Wide Range ◽  
The Galaxy

AbstractThe initial mass function (IMF) is an essential tool with which to study star formation processes. We have initiated the photometric survey of young open clusters in the Galaxy, from which the stellar IMFs are obtained in a homogeneous way. A total of 16 famous young open clusters have preferentially been studied up to now. These clusters have a wide range of surface densities (log σ = −1 to 3 [stars pc−2] for stars with mass larger than 5M⊙) and cluster masses (Mcl = 165 to 50, 000M⊙), and also are distributed in five different spiral arms in the Galaxy. It is possible to test the dependence of star formation processes on the global properties of individual clusters or environmental conditions. We present a preliminary result on the variation of the IMF in this paper.

scholarly journals Mass Segregation in the Young SMC Cluster NGC 330

2002 ◽  
Vol 207 ◽  
pp. 687-690
Author(s):  
Marco Sirianni ◽  
Antonella Nota ◽  
Guido De Marchi ◽  
Claus Leitherer ◽  
Mark Clampin
Keyword(s):  
Luminosity Function ◽  
Radial Distance ◽  
Mass Range ◽  
Mass Function ◽  
Young Star ◽  
Initial Mass Function ◽  
Cluster Center ◽  
Central Regions ◽  
Mass Segregation ◽  
The Imf

We present a new study of the low end of the stellar IMF of NGC 330, the richest young star cluster in the Small Magellanic Cloud (SMC). Using deep broadband images taken with the HST/WFPC2 we have derived the cluster's luminosity function and constructed the initial mass function (IMF) in the mass range 1 − 7M⊙. We have investigated the IMF as a function of the radial distance from the cluster center. We find that, after correction for background contamination, the IMF is fairly homogeneous with a slope slightly steeper than Salpeter's in the central regions of the cluster (< 40″) but becomes increasingly steeper with distance, indicating a preponderance of massive stars in the core of the cluster. NGC 330 is one of the first clusters for which evidence of mass segregation is directly found.

scholarly journals Structure and Mass Function of Open Cluster NGC 6910

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Harmeen Kaur ◽  
Saurabh Sharma ◽  
Alok K. Durgapal
Keyword(s):  
Molecular Clouds ◽  
Luminosity Function ◽  
Open Cluster ◽  
Mass Function ◽  
Open Clusters ◽  
Initial Mass Function ◽  
Wide Field ◽  
Evolutionary Models ◽  
Star Forming ◽  
Initial Results

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.

scholarly journals Structure and Mass Function of Open Cluster NGC 6910

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Harmeen Kaur ◽  
Saurabh Sharma ◽  
Alok K. Durgapal
Keyword(s):  
Molecular Clouds ◽  
Luminosity Function ◽  
Open Cluster ◽  
Mass Function ◽  
Open Clusters ◽  
Initial Mass Function ◽  
Wide Field ◽  
Evolutionary Models ◽  
Star Forming ◽  
Initial Results

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

scholarly journals Variation in the Stellar Initial Mass Function from the Chromospheric Activity of M Dwarfs in Early-type Galaxies

2021 ◽  
Vol 923 (1) ◽  
pp. 43
Author(s):  
Pieter van Dokkum ◽  
Charlie Conroy
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Early Type ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Chromospheric Activity ◽  
Stellar Initial Mass Function ◽  
Low Mass ◽  
The Imf

Abstract Mass measurements and absorption-line studies indicate that the stellar initial mass function (IMF) is bottom-heavy in the central regions of many early-type galaxies, with an excess of low-mass stars compared to the IMF of the Milky Way. Here we test this hypothesis using a method that is independent of previous techniques. Low-mass stars have strong chromospheric activity characterized by nonthermal emission at short wavelengths. Approximately half of the UV flux of M dwarfs is contained in the λ1215.7 Lyα line, and we show that the total Lyα emission of an early-type galaxy is a sensitive probe of the IMF with a factor of ∼2 flux variation in response to plausible variations in the number of low-mass stars. We use the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure the Lyα line in the centers of the massive early-type galaxies NGC 1407 and NGC 2695. We detect Lyα emission in both galaxies and demonstrate that it originates in stars. We find that the Lyα to i-band flux ratio is a factor of 2.0 ± 0.4 higher in NGC 1407 than in NGC 2695, in agreement with the difference in their IMFs as previously determined from gravity-sensitive optical absorption lines. Although a larger sample of galaxies is required for definitive answers, these initial results support the hypothesis that the IMF is not universal but varies with environment.

scholarly journals The Initial Mass Function of Be Stars

2004 ◽  
Vol 215 ◽  
pp. 83-84
Author(s):  
J. Zorec ◽  
R. Levenhagen ◽  
J. Chauville ◽  
Y. Frémat ◽  
D. Ballereau ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Be Stars ◽  
Fast Rotation ◽  
Formation Conditions ◽  
The Imf

Allowing for systematic differences in the counting of Be Stars due to their overluminosity, changes produced by their fast rotation on spectral types and time spent in the main sequence, a difference between the IMF (Be) and IMF(B) appears, which indicates that the appearance of the Be phenomenon may relay on differences in the initial star formation conditions.

scholarly journals Star Formation in Cooling Flows

1987 ◽  
Vol 127 ◽  
pp. 167-177
Author(s):  
R. W. O'Connell
Keyword(s):  
Star Formation ◽  
Stellar Populations ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Flow Forming ◽  
Cooling Flows ◽  
Cd Galaxies ◽  
Ngc 1275 ◽  
The Imf

Star formation, probably with an abnormal initial mass function, represents the most plausible sink for the large amounts of material being accreted by cD galaxies from cooling flows. There are three prominent cases (NGC 1275, PKS 0745-191, and Abell 1795) where cooling flows have apparently induced unusual stellar populations. Recent studies show that about 50% of other accreting cD's have significant ultraviolet excesses. It therefore appears that detectable accretion populations are frequently associated with cooling flows. The questions of the form of the IMF, the fraction of the flow forming stars, and the lifetime of the flow remain open.

scholarly journals On the Bulk Yields of Nucleosynthesis from Massive Stars

1977 ◽  
Vol 45 ◽  
pp. 161-164
Author(s):  
W. David Arnett
Keyword(s):  
Solar System ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Iron Group ◽  
Helium Stars ◽  
The Absolute ◽  
The Imf

Preliminary estimates are made of the absolute yields of abundant nuclei synthesized in observed stars. The compositions of helium stars of mass 3 ≤ Mα / Mʘ≤ 64 are presented, taken at the instant of instability. These stars of mass Mα are identified with stars of main sequence mass M. The amount of synthesized matter for each mass M ≥ MʘHe is estimated (Table 1). Using a variety of choices for the initial mass function (IMF) the yield per stellar generation is calculated. For standard choices of the IMF the absolute and relative yields of12C,16O,20Ne,24Mg, the Si to Ca group and the iron group agree with solar system values, to the accuracy of the calculations.

scholarly journals Stellar velocity dispersion and initial mass function gradients in dissipationless galaxy mergers

2020 ◽  
Vol 499 (1) ◽  
pp. 559-572
Author(s):  
Carlo Nipoti ◽  
Carlo Cannarozzo ◽  
Francesco Calura ◽  
Alessandro Sonnenfeld ◽  
Tommaso Treu
Keyword(s):  
Velocity Dispersion ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Galaxy Mergers ◽  
Orbital Parameters ◽  
Spatially Resolved ◽  
Stellar Velocity ◽  
Stellar Initial Mass Function ◽  
The Imf

ABSTRACT The stellar initial mass function (IMF) is believed to be non-universal among early-type galaxies (ETGs). Parametrizing the IMF with the so-called IMF mismatch parameter αIMF, which is a measure of the stellar mass-to-light ratio of an ensemble of stars and thus of the ‘heaviness’ of its IMF, one finds that for ETGs αe (i.e. αIMF integrated within the effective radius Re) increases with σe (the line-of-sight velocity dispersion σlos integrated within Re) and that, within the same ETG, αIMF tends to decrease outwards. We study the effect of dissipationless (dry) mergers on the distribution of the IMF mismatch parameter αIMF in ETGs using the results of binary major and minor merging simulations. We find that dry mergers tend to make the αIMF profiles of ETGs shallower, but do not alter significantly the shape of the distributions in the spatially resolved σlos–αIMF space. Individual galaxies undergoing dry mergers tend to decrease their αe, due to erosion of αIMF gradients and mixing with stellar populations with lighter IMF. Their σe can either decrease or increase, depending on the merging orbital parameters and mass ratio, but tends to decrease for cosmologically motivated merging histories. The αe–σe relation can vary with redshift as a consequence of the evolution of individual ETGs: based on a simple dry-merging model, ETGs of given σe are expected to have higher αe at higher redshift, unless the accreted satellites are so diffuse that they contribute negligibly to the inner stellar distribution of the merger remnant.

scholarly journals The Initial Mass Function in Young Star Clusters

1986 ◽  
Vol 7 ◽  
pp. 489-499
Author(s):  
Hans Zinnecker
Keyword(s):  
Star Formation ◽  
Recent Work ◽  
Star Clusters ◽  
Mass Function ◽  
Young Star ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Stellar Content ◽  
Young Star Clusters ◽  
The Imf

AbstractThis review discusses both the earlier and the most recent work on the IMF in young star clusters. It is argued that the study of the stellar content of young star clusters offers the best chance of developing a theory of star formation and of the IMF.

Sign in / Sign up

Export Citation Format

Share Document