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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 article, the broadband photometric evolution of unresolved star clusters is calculated in a simplified way, including the preferential loss of low-mass stars due to mass segregation, which results in a narrowing of the stellar mass range.
Abstract: The broad-band photometric evolution of unresolved star clusters is calculated in a simplified way, including the preferential loss of low-mass stars due to mass segregation. The stellar mass function of a cluster evolves due to three effects: (a) the evolution of the massive stars reduces their number; (b) tidal effects before cluster-wide mass segregation reduce the mass function homogeneously, i.e. independently of the stellar mass; (c) after mass segregation has finished, tidal effects preferentially remove the lowest-mass stars from the cluster. These effects result in a narrowing of the stellar mass range. These effects are described quantitatively, following the results of N-body simulations, and are taken into account in the calculation of the photometric history, based on the galev cluster evolution models for solar metallicity and a Salpeter mass function. We find the following results: (1) During the first ∼40% of the lifetime of a cluster its colour evolution is adequately described by the standard galev models (without mass segregation) but the cluster becomes fainter due to the loss of stars by tidal effects. (2) Between ∼40 and ∼80% of its lifetime (independent of the total lifetime), the cluster becomes bluer due to the loss of low-mass stars. This will result in an underestimate of the age of clusters if standard cluster evolution models are used. (3) After ∼80% of the total lifetime of a cluster it will rapidly become redder. This will result in an overestimate of the age of clusters if standard cluster evolution models are used. (4) Clusters with mass segregation and the preferential loss of low-mass stars evolve along almost the same tracks in colour–colour diagrams as clusters without mass segregation. Only if the total lifetime of clusters can be estimated can the colours be used to give reliable age estimates. (5) The changes in the colour evolution of unresolved clusters due to the preferential loss of low-mass stars will affect the determination of the star formation histories of galaxies if they are derived from clusters that have a total lifetime of less than about 30 Gyr. (6) The preferential loss of low-mass stars might explain the presence of old (∼13 Gyr) clusters in NGC 4365 which are photometrically disguised as intermediate-age clusters (2–5 Gyr), if the expected total lifetime of these clusters is between 16 and 32 Gyr.

32 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used deep WFPC2 F555W and F814W photometry to determine the main sequence luminosity functions both near the cluster center and in a field near the half-light radius.
Abstract: A low mass, large core radius, and strong tidal tails suggest that the globular cluster Palomar 5 has lost a large fraction of its initial mass over time. If the dynamical evolution of Palomar 5 has been dominated by the effects of mass loss, then the luminosity function should be deficient in low-mass stars. Using deep WFPC2 F555W and F814W photometry, we determine the main sequence luminosity functions both near the cluster center and in a field near the half-light radius. There is no compelling evidence for mass segregation within the cluster, but a comparison of the global mass function of Palomar 5 with those of Omega Cen and M55 indicates an increasing deficiency of stars with progressively lower masses. A fit of the observed luminosity function to theoretical models yields a power-law mass function with an exponent of -0.5. The flatness of the mass function is consistent with models of the dynamical evolution of globular clusters that have lost on the order of 90% of their original stellar mass. We suggest that Palomar 5 has lost a large percentage of its original stellar content as a result of tidal shocking.

32 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the evolution of the mass function in young and dense star clusters by means of direct N-body simulations and showed that the Arches initial mass function is consistent with a Salpeter slope down to ∼1.
Abstract: We study the evolution of the mass function in young and dense star clusters by means of direct N-body simulations. Our main aim is to explain the recent observations of the relatively flat mass function observed near the centre of the Arches star cluster. In this region, the power-law index of the mass function for stars more massive than about 5–6 M⊙ is larger than the Salpeter value by about unity, whereas further out, and for the lower mass stars, the mass function resembles the Salpeter distribution. We show that the peculiarities in the Arches mass function can be explained satisfactorily without primordial mass segregation. We draw two conclusions from our simulations: (i) the Arches initial mass function is consistent with a Salpeter slope down to ∼1 M⊙, and (ii) the cluster is about half-way towards core collapse. The cores of other star clusters with characteristics similar to those of the Arches are expected to show similar flattening in the mass functions for the high-mass (≳5 M⊙) stars.

32 citations

Journal ArticleDOI
TL;DR: In this article, the Orion A molecular cloud is one of the most well-studied nearby star-forming regions, and includes regions of both highly clustered and more dispersed star formation across its full extent.
Abstract: The Orion A molecular cloud is one of the most well-studied nearby star-forming regions, and includes regions of both highly clustered and more dispersed star formation across its full extent. Here, we analyze dense, star-forming cores identified in the 850 and 450 μm SCUBA-2 maps from the JCMT Gould Belt Legacy Survey. We identify dense cores in a uniform manner across the Orion A cloud and analyze their clustering properties. Using two independent lines of analysis, we find evidence that clusters of dense cores tend to be mass segregated, suggesting that stellar clusters may have some amount of primordial mass segregation already imprinted in them at an early stage. We also demonstrate that the dense core clusters have a tendency to be elongated, perhaps indicating a formation mechanism linked to the filamentary structure within molecular clouds.

31 citations

Journal ArticleDOI
TL;DR: In this article, the authors used a combination of the Hubble Space Telescope and ground-based data to probe the dynamical state of the low mass Galactic globular cluster NGC 6101.
Abstract: We used a combination of Hubble Space Telescope and ground based data to probe the dynamical state of the low mass Galactic globular cluster NGC 6101. We have re-derived the structural parameters of the cluster by using star counts and we find that it is about three times more extended than thought before. By using three different indicators, namely the radial distribution of Blue Straggler Stars, that of Main Sequence binaries and the luminosity (mass) function, we demonstrated that NGC 6101 shows no evidence of mass segregation, even in the innermost regions. Indeed, both the BSS and the binary radial distributions fully resemble that of any other cluster population. In addition the slope of the luminosity (mass) functions does not change with the distance, as expected for non relaxed stellar systems. NGC 6101 is one of the few globulars where the absence of mass segregation has been observed so far. This result provides additional support to the use of the "dynamical clock" calibrated on the radial distribution of the Blue Stragglers as a powerful indicator of the cluster dynamical age.

31 citations


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