scispace - formally typeset
Search or ask a question
Topic

Mass segregation

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


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, proper motions and membership probabilities of 364 stars in the open cluster NGC 6530 region are reduced on the basis of membership determination, luminosity function and segregation effect of the cluster.
Abstract: From photographic plate data of Shanghai Astronomical Observatory with a time baseline of 87 years, proper motions and membership probabilities of 364 stars in the open cluster NGC 6530 region are reduced. On the basis of membership determination, luminosity function and segregation effect of the cluster are discussed with details. Spatial mass segregation is obviously present in NGC 6530 while there is no clear evidence for a velocity-mass (or velocity-luminosity) dependence. The observed spatial mass segregation for NGC 6530 might be due to a combination of initial conditions and relaxation process.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed proper motions from the Hubble Space Telescope (HST) and the second Gaia data release along with line-of-sight velocities from the MUSE spectrograph to detect imprints of an intermediate-mass black hole (IMBH) in the center of the nearby, core-collapsed, globular cluster NGC 6397.
Abstract: We analyze proper motions from the Hubble Space Telescope (HST) and the second Gaia data release along with line-of-sight velocities from the MUSE spectrograph to detect imprints of an intermediate-mass black hole (IMBH) in the center of the nearby, core-collapsed, globular cluster NGC 6397. For this, we use the new MAMPOSSt-PM Bayesian mass-modeling code, along with updated estimates of the surface density profile of NGC 6397. We consider different priors on velocity anisotropy and on the size of the central mass, and we also separate the stars into components of different mean mass to allow for mass segregation. The velocity ellipsoid is very isotropic throughout the cluster, as expected in post-core collapsed clusters subject to as strong a Galactic tidal field as NGC 6397. There is strong evidence for a central dark component of 0.8 to 2% of the total mass of the cluster. However, we find robust evidence disfavoring a central IMBH in NGC 6397, preferring instead a diffuse dark inner subcluster of unresolved objects with a total mass of 1000 to 2000 solar masses, half of which is concentrated within 6 arcsec (2% of the stellar effective radius). These results require the combination of HST and Gaia data: HST for the inner diagnostics and Gaia for the outer surface density and velocity anisotropy profiles. The small effective radius of the diffuse dark component suggests that it is composed of compact stars (white dwarfs and neutron stars) and stellar-mass black holes, whose inner locations are caused by dynamical friction given their high progenitor masses. We show that stellar-mass black holes should dominate the mass of this diffuse dark component, unless more than 25 per cent escape from the cluster. Their mergers in the cores of core-collapsed globular clusters could be an important source of the gravitational wave events detected by LIGO.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the mass functions φ(M) = dN/dM ∝ M ―∝ of a sample of nine clusters of ages varying from 4 Myr to 1.2 Gyr and Galactocentric distances from 6 to 12 kpc were studied.
Abstract: In this paper, using the Two Micron All Sky Survey (2MASS) photometry, we study the mass functions φ(M) = dN/dM ∝ M ―∝ of a sample of nine clusters of ages varying from 4 Myr to 1.2 Gyr and Galactocentric distances from 6 to 12 kpc. We look for evidence of mass segregation in these clusters by tracing the variation in the value of α in different regions of the cluster as a function of the parameter τ = t age /t relax (where t age is the age of the cluster and t relax is the relaxation time of the cluster), Galactocentric distance, age and size of the cluster. The value of α value increases with age and τ and fits straight lines with slopes m and y-intercepts c given by m = 0.40 ± 0.03, c = -1.86 ± 0.27 and m = 0.01 ± 0.001, c = ―0.85 ± 0.02, respectively, and is a clear indicator of the dynamical processes involved. The confidence level of the Pearson's product-moment correlation of α with age is 0.76 with p = 0.002 and with τ is 0.71 with p = 0.007. The value of α also increases with Galactocentric distance, indicating the presence of a larger relative number of low-mass stars in clusters at larger Galactocentric distances. We find two clusters, namely IC 1805 and NGC 1893, with evidence of primordial or early dynamical mass segregation. Implications of primordial mass segregation on the formation of massive stars and recent results supporting early dynamical mass segregation are discussed.

16 citations

Posted Content
TL;DR: In this paper, 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 luminosity functions with M* = -195 + 5 log h, and alpha = -10, where M* and alpha are the usual parameters in the standard Schechter form of the Luminosity function, and the magnitudes are measured in the B band.
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* = -195 + 5 log h, and alpha = -10, where M* and alpha 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 alpha range from (-193,-08), to (-197,-12) 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

16 citations

Journal ArticleDOI
TL;DR: In this paper, a set of deep B-and V-band images of the central density cusp of the globular cluster M30 (NGC 7099), taken with the Faint Object Camera aboard the Hubble Space Telescope, were analyzed.
Abstract: We begin by presenting the analysis of a set of deep B- and V-band images of the central density cusp of the globular cluster M30 (NGC 7099), taken with the Faint Object Camera aboard the Hubble Space Telescope. These images are the first to resolve lower-mass main-sequence stars in the cluster's central 10''. From the positions of individual stars, we measure an improved position for the cluster center; this new position is 2.6'' from the previously known position. We find no evidence of a ``flat'', constant-surface-density core; however, the data do not rule out the presence of a core of radius up to 1.9'' (95% confidence level). We measure a logarithmic cusp slope (d \log \sigma / d \log r$) of -0.76 +- 0.07 (1-sigma) for stars with masses between 0.69 and 0.76 \Msun, and -0.82 +- 0.11 for stars with masses between 0.57 and 0.69 \Msun. We also compare the overall mass function (MF) of the cluster cusp with the MF of a field at r = 4.6' (near the cluster half-mass radius). The observed degree of mass segregation is well matched by the predictions of an isotropic, multimass King model. We then use the Jeans equation to compare the structure of M30 with that of M15, another cusped cluster, using data from this and a previous paper. We find that M30 is very close to achieving equipartition of energy between stellar species, at least over the observed range in mass and radius, while M15 is not. This difference may be a result of the longer relaxation time in the observed field in M15. The data also suggest that the degree of mass segregation within the two cluster cusps is smaller than one would expect from the measurements at larger radius. If so, this phenomenon might be the result of gravothermal oscillations, of centrally-concentrated populations of binaries, or of a ~10^3 \Msun black hole in one or more clusters.

16 citations


Network Information
Related Topics (5)
Star formation
37.4K papers, 1.8M citations
94% related
Galaxy
109.9K papers, 4.7M citations
94% related
Active galactic nucleus
20.7K papers, 996.7K citations
94% related
Elliptical galaxy
20.9K papers, 1M citations
94% related
Metallicity
19.4K papers, 966.7K citations
93% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202336
202225
202133
202047
201943
201822