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Mass segregation

About: Mass segregation is a research topic. Over the lifetime, 1024 publications have been published within this topic receiving 57729 citations.


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Journal ArticleDOI
Long Wang1
TL;DR: In this paper, the authors investigate the energy balance between the BH subsystem and the global, and find that to properly describe the evolution of clusters, a corrected two-body relaxation time, $T_{rh,p} = T_{rh}/psi$ is necessary.
Abstract: Recent observations have detected top-heavy IMFs in dense star forming regions like the Arches cluster. Whether such IMFs also exist in old dense stellar systems like globular clusters is difficult to constrain, because massive stars already became black holes (BHs) and neutron stars (NSs). However, studies of stellar dynamics find that BHs/NSs influence the long-term evolution of star clusters. Following Breen & Heggie (2013) and by carrying out two-component $N$-body simulations, we demonstrate how this dynamical impact connects with the shape of IMFs. By investigating the energy balance between the BH subsystem and the global, we find that to properly describe the evolution of clusters, a corrected two-body relaxation time, $T_{rh,p} = T_{rh}/\psi$, is necessary. Because $\psi$ depends on the total mass fraction of BHs, $M_2 / M$, and the mass ratio, $m_2 / m_1$, the cluster dissolution time is sensitive to the property of BHs or IMFs. Especially, the escape rate of BHs via ejections from few-body encounters is linked to mass segregation. In strong tidal fields, top-heavy IMFs easily lead to the fast dissolution of star clusters and the formation of BH-dominant dark clusters, which suggests that the observed massive GCs with dense cores are unlikely to have extreme top-heavy IMFs. With the future observations of gravitational waves providing unique information of BHs/NSs, it is possible to combine the multi-message observations to have better constrains on the IMFs of old star clusters.

22 citations

Journal ArticleDOI
TL;DR: In this paper, a two-component cluster consisting of two types of stars with different masses is considered, and the authors trace the overall behaviors of the probability distribution functions of the two components and obtain the timescale of mass segregation as a simple function of the cluster parameters.
Abstract: Mass segregation in a star cluster is studied in an analytical manner. We consider a two-component cluster, which consists of two types of stars with different masses. Plummer's model is used for the initial condition. We trace the overall behaviors of the probability distribution functions of the two components and obtain the timescale of mass segregation as a simple function of the cluster parameters. The result is used to discuss the origin of a black hole with mass of > 1000 M(sun) found in the starburst galaxy M82.

22 citations

Posted Content
Stephen E. Zepf1
01 Jan 2013
TL;DR: Zepf et al. as discussed by the authors studied the luminosity function of galaxies in the Hickson groups using their recent redshift survey of galaxies and found that the galaxies in these regions have a luminosity functions with M∗ = −19.5 + 5logh, and α = −1.0.
Abstract: We study the luminosity function of galaxies in Hickson groups using our recent redshift survey of galaxies in and around 17 of these groups. We find that the galaxies in these regions have a luminosity function with M∗ = −19.5 + 5logh, and α = −1.0, where M∗ and α are the usual parameters in the standard Schechter form of the luminosity function, and the magnitudes are measured in the B band. The formal 95% confidence intervals for M∗ and α range from (-19.3,-0.8), to (-19.7,-1.2) and are highly correlated as is usual for these fits. This luminosity function for galaxies in our Hickson group sample is very similar from that found in large surveys covering a range of environments. These values are also consistent with our earlier estimates based on a photometric analysis with statistical background correction, and do not support previous suggestions of an underabundance of intrinsically faint galaxies in compact groups. We confirm our earlier finding that the fainter galaxies are more diffusely distributed within individual groups than the brighter ones. This can be interpreted either as evidence for mass segregation within the groups or as the result of the selection procedure for Hickson groups. Subject headings: galaxies: clusters – galaxies: interactions – galaxies: luminosity function – galaxies: statistics Hubble Fellow e-mail:zepf@astro.yale.edu

21 citations

Journal ArticleDOI
TL;DR: This paper examined the level of substructure and mass segregation in the massive, young cluster Westerlund 1 and found that it is relatively smooth, with little or no mass segregation, but with the massive stars in regions of significantly higher than average surface density.
Abstract: We examine the level of substructure and mass segregation in the massive, young cluster Westerlund 1. We find that it is relatively smooth, with little or no mass segregation, but with the massive stars in regions of significantly higher than average surface density. While an expanding or bouncing-back scenario for the evolution of Westerlund 1 cannot be ruled out, we argue that the most natural model to explain these observations is one in which Westerlund 1 formed with no primordial mass segregation and at a similar or larger size than we now observe.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the two Large Magellanic Cloud star clusters NGC1805 and NGC 1818 are approximately the same chronological age (30 Myr), but show different radial trends in binary frequency.
Abstract: The two Large Magellanic Cloud star clusters NGC 1805 and NGC 1818 are approximately the same chronological age (�30 Myr), but show different radial trends in binary frequency. The F-type stars (1.3 - 2.2 M⊙) in NGC 1818 have a binary frequency that decreases towards the core, while the binary frequency for stars of similar mass in NGC 1805 is flat with radius, or perhaps bimodal (with a peak in the core). We show here, through detailed N-body modeling, that both clusters could have formed with the same primordial binary frequency and with binary orbital elements and masses drawn from the same distributions (defined from observations of open clusters and the field of our Galaxy). The observed radial trends in binary frequency for both clusters are best matched with models that have initial substructure. Furthermore, both clusters may be evolving along a very similar dynamical sequence, with the key difference that NGC 1805 is dynamically older than NGC 1818. The F-type binaries in NGC 1818 still show evidence of an initial period of rapid dynamical disruptions (which occur preferentially in the core), while NGC 1805 has already begun to recover a higher core binary frequency, owing to mass segregation (which will eventually produce a distribution in binary frequency that rises only towards the core, as is observed in old Milky Way star clusters). This recovery rate increases for higher-mass binaries, and therefore even at one age in one cluster, we predict a similar dynamical sequence in the radial distribution of the binary frequency as a function of binary primary mass.

21 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202336
202225
202133
202047
201943
201822