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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
TL;DR: In this paper, the appearance of the white dwarf population in dense star clusters was investigated using realistic N-body simulations and it was shown that the presence of a substantial binary population in a star cluster, and the interaction of this population with the cluster environment, has serious consequences for the morphology of the observed white dwarf sequence and the derived white dwarf cooling age of the cluster.
Abstract: We use the results of realistic N-body simulations to investigate the appearance of the white dwarf population in dense star clusters. We show that the presence of a substantial binary population in a star cluster, and the interaction of this population with the cluster environment, has serious consequences for the morphology of the observed white dwarf sequence and the derived white dwarf cooling age of the cluster. We find that over time the dynamical evolution of the cluster?mass segregation, stellar interactions, and tidal stripping?hampers the use of white dwarfs as tracers of the initial mass function and also leads to a significant enhancement of the white dwarf mass fraction. Future observations of star clusters should be conducted slightly interior to the half-mass radius of the cluster in order to best obtain information about the cluster age and initial mass function from the white dwarf luminosity function. The evolution of binary stars and the cluster environment must necessarily be accounted for when the white dwarf populations of dynamically evolved star clusters are studied.

60 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a catalogue of R c I c Z photometry over an area of 0.855 square degrees, centred on the young open cluster NGC 2547.
Abstract: We present a catalogue of R c I c Z photometry over an area of 0.855 square degrees, centred on the young open cluster NGC 2547. The survey is substantially complete to limits of R c = 21.5, I c = 19.5, Z = 19.5. We use the catalogue to define a sample of NGC 2547 candidates with model-dependent masses of about 0.05 -1.0 M ○. . After correcting for incompleteness and estimating contamination by foreground field dwarfs, we investigate the mass function of the cluster, its binary content, and search for evidence of mass segregation among the lower mass stars. There is ample evidence for mass segregation between high (>3 M ○. ) and lower mass stars, but over the range 0.1 < M < 0.7 M ○. , the data are consistent with no further mass segregation. By fitting King profiles we conclude that at least 60 per cent of the low-mass stellar population are contained within our survey. The cluster mass function is remarkably similar to the Pleiades for 0.075 < M < 0.7 M ○. . Because of its age (≃ 30 Myr), we demonstrate that this mass function is robust to a number of systematic uncertainties likely to affect older and younger clusters and is therefore one of the best available estimates for the initial mass function in young disc populations. For 0.05 < M < 0.075 M ○. there is some evidence for a deficit of brown dwarfs in NGC 2547 compared with other clusters. This deficit may extend to lower masses or may only be a dip, perhaps caused by an imperfect understanding of the mass-magnitude relationship at temperatures of around 2800 K. Incompleteness in both our survey and the luminosity functions from which we estimate contamination by foreground objects leave this question open. The binary fraction for systems with mass ratios greater than about 0.5 is 20-35 per cent for M dwarfs in NGC 2547, quite consistent with that found in the field and other young clusters. The full photometric catalogue and our lists of candidate cluster members are made available in electronic format.

60 citations

Journal ArticleDOI
TL;DR: In this article, the authors performed a kinematic and photometric selection using the PPMXL and Pan-STARRS1 sky surveys, to search for cluster members up to 30 pc from the cluster center.
Abstract: The Hyades cluster is an ideal target to study the dynamical evolution of a star cluster over the entire mass range due to its intermediate age and proximity to the Sun. We wanted to extend the Hyades mass function towards lower masses down to 0.1 Msol and to use the full three-dimensional spatial information to characterize the dynamical evolution of the cluster. We performed a kinematic and photometric selection using the PPMXL and Pan-STARRS1 sky surveys, to search for cluster members up to 30 pc from the cluster centre. We determined our detection efficiency and field star contamination rate to derive the cluster luminosity and mass functions down to masses of 0.1 Msol. The thorough astrometric and photometric constraints minimized the contamination. A minimum spanning tree algorithm was used to quantify the mass segregation. We discovered 43 new Hyades member candidates with velocity perpendicular to the Hyades motion up to 2 km/s. They have mass estimates between 0.43 and 0.09 Msol, for a total mass of 10 Msol. This doubles the number of Hyades candidates with masses smaller than 0.15 Msol. We provide an additional list of 11 possible candidates with velocity perpendicular to the Hyades motion up to 4 km/s. The cluster is significantly mass segregated. The extension of the mass function towards lower masses provided an even clearer signature than estimated in the past. We also identified as likely Hyades member an L0 dwarf previously assumed to be a field dwarf. Finally we question the membership of a number of previously published candidates, including a L2.5-type dwarf.

59 citations

Journal ArticleDOI
TL;DR: In this paper, the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831, a rich star cluster in the LMC, is presented.
Abstract: We present the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831, a rich star cluster in the LMC. The data were obtained with HST/WFPC2 in the F555W (V) and F814W (I) filters, reaching m555 25. We discuss and apply a method of correcting the CMD for sampling incompleteness and field star contamination. Ecient use of the CMD data was made by means of direct comparisons of the observed to model CMDs. The model CMDs are built by an algorithm that generates artificial stars from a single stellar population, characterized by an age, a metallicity, a distance, a reddening value, a present day mass function and a fraction of unresolved binaries. Photometric uncertainties are empirically determined from the data and incorporated into the models as well. Statistical techniques are presented and applied as an objective method to assess the compatibility between the model and data CMDs. By modelling the CMD of the central region in NGC 1831 we infer a metallicity Z = 0:012, 8:75 log (=yr) 8:80, 18:54 (m M)0 18:68 and 0:00 E(B V) 0:03. For the position dependent PDMF slope (= dl og(M)= dl ogM), we clearly observe the eect of mass segregation in the system: for projected distances R 30 arcsec,' 1:7, whereas 2:2 2:5 in the outer regions of NGC 1831.

59 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of radial anisotropy and mass segregation on the appearance of stellar-mass black holes in the center of globular clusters and showed that the best fit model includes a smaller population of remnants, and a less extreme degree of anisotropic variation.
Abstract: The search for intermediate-mass black holes (IMBHs) in the centre of globular clusters is often based on the observation of a central cusp in the surface brightness profile and a rise towards the centre in the velocity dispersion profiles. Similar signatures, however, could result from other effects, that need to be taken into account in order to determine the presence (or the absence) of an IMBH in these stellar systems. Following our previous exploration of the role of radial anisotropy in shaping these observational signatures, we analyse here the effects produced by the presence of a population of centrally concentrated stellar-mass black holes. We fit dynamical models to ω Cen data, and we show that models with ~ 5% of their mass in black holes (consistent with ~ 100% retention fraction after natal kicks) can reproduce the data.When simultaneously considering both radial anisotropy and mass segregation, the bestfit model includes a smaller population of remnants, and a less extreme degree of anisotropy with respect to the models that include only one of these features. These results underline that before conclusions about putative IMBHs can be made, the effects of stellar-mass black holes and radial anisotropy need to be properly accounted for.

58 citations


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