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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 authors compared the evolution of representative clusters in the mass and concentration basis in the vicinity of a supermassive black hole and used the spatial distribution, density profile, and the $50\%$ Lagrange radius as indicators along the complete simulation to study the evolutionary shape in physical and velocity space and the final fate of these representative clusters.
Abstract: The infall and merger scenario of massive clusters in the Milky Way's potential well, as one of the Milky Way formation mechanisms, is reexamined to understand how the stars of the merging clusters are redistributed during and after the merger process using, for the first time, simulations with a high resolution concentrated in the 300 pc around the Galactic center. We adopted simulations developed in the framework of the"Modelling the Evolution of Galactic Nuclei"(MEGaN) project. We compared the evolution of representative clusters in the mass and concentration basis in the vicinity of a supermassive black hole. We used the spatial distribution, density profile, and the $50\%$ Lagrange radius (half mass radius) as indicators along the complete simulation to study the evolutionary shape in physical and velocity space and the final fate of these representative clusters. We detect that the least massive clusters are quickly (<10 Myr) destroyed. Instead, the most massive clusters have a long evolution, showing variations in the morphology, especially after each passage close to the supermassive black hole. The deformation of the clusters depends on the concentration, with general deformations for the least concentrated clusters and outer strains for the more concentrated ones. At the end of the simulation, a dense concentration of stars belonging to the clusters is formed. The particles that belong to the most massive and most concentrated clusters are concentrated in the innermost regions, meaning that the most massive and concentrated clusters contribute with a more significant fraction of particles to the final concentration, which suggests that the population of stars of the nuclear star cluster formed through this mechanism comes from massive clusters rather than low-mass globular clusters.
Posted ContentDOI
16 Feb 2023
TL;DR: In this paper , the morphological evolution of embedded star clusters in the earliest stages of their evolution is investigated using Torch, which uses the AMUSE framework to couple state-of-theart stellar dynamics to star formation, radiation, stellar winds, and hydrodynamics in FLASH.
Abstract: We perform simulations of star cluster formation to investigate the morphological evolution of embedded star clusters in the earliest stages of their evolution. We conduct our simulations with Torch, which uses the AMUSE framework to couple state-of-the-art stellar dynamics to star formation, radiation, stellar winds, and hydrodynamics in FLASH. We simulate a suite of $10^4$ M$_{\odot}$ clouds at 0.0683 pc resolution for $\sim$ 2 Myr after the onset of star formation, with virial parameters $\alpha$ = 0.8, 2.0, 4.0 and different random samplings of the stellar initial mass function and prescriptions for primordial binaries. Our simulations result in a population of embedded clusters with realistic morphologies (sizes, densities, and ellipticities) that reproduce the known trend of clouds with higher initial $\alpha$ having lower star formation efficiencies. Our key results are as follows: (1) Cluster mass growth is not monotonic, and clusters can lose up to half of their mass while they are embedded. (2) Cluster morphology is not correlated with cluster mass and changes over $\sim$ 0.01 Myr timescales. (3) The morphology of an embedded cluster is not indicative of its long-term evolution but only of its recent history: radius and ellipticity increase sharply when a cluster accretes stars. (4) The dynamical evolution of very young embedded clusters with masses $\lesssim$ 1000 M$_{\odot}$ is dominated by the overall gravitational potential of the star-forming region rather than by internal dynamical processes such as two- or few-body relaxation.
Journal ArticleDOI
TL;DR: In this paper, the authors examined the impact of massive stars to their environment and found that the photoionized gas associated with the cluster is the dominant feedback mechanism in the cluster, which is supported with evidence of the observed age gradient between the cluster and the powering sources of the radio clumps.
Abstract: Deep and wide-field optical photometric observations along with multiwavelength archival datasets have been employed to study the physical properties of the cluster NGC 6910. The study also examines the impact of massive stars to their environment. The age, distance and reddening of the cluster are estimated to be $\sim$4.5 Myr, $1.72\pm0.08$ kpc, and $ E(B-V)_{min}= 0.95$ mag, respectively. The mass function slope ($\Gamma = -0.74\pm0.15$ in the cluster region is found to be flatter than the Salpeter value (-1.35), indicating the presence of excess number of massive stars. The cluster also shows mass segregation towards the central region due to their formation processes. The distribution of warm dust emission is investigated towards the central region of the cluster, showing the signature of the impact of massive stars within the cluster region. Radio continuum clumps powered by massive B-type stars (age range $\sim$ 0.07-0.12 Myr) are traced, which are located away from the center of the stellar cluster NGC 6910 (age $\sim$ 4.5 Myr). Based on the values of different pressure components exerted by massive stars, the photoionized gas associated with the cluster is found to be the dominant feedback mechanism in the cluster. Overall, the massive stars in the cluster might have triggered the birth of young massive B-type stars in the cluster. This argument is supported with evidence of the observed age gradient between the cluster and the powering sources of the radio clumps.
01 Jan 2010
TL;DR: In this article, a photometric catalog of a cluster was used to determine the mass distribution of its members, including single stars and both components of binary systems, and the spatial distribution of the cluster members.
Abstract: Despite being some of the most familiar objects observed in the sky, much remains unknown about open clusters. The theory of their formation admits many unanswered questions, and the complex dynamics of their evolution remains an extremely difficult problem to address. In this thesis, I present results that both help to constrain formation theories, as well as to shed new understanding on the many physical processes that drive their evolution.Starting with a photometric catalog of a cluster, I employ a maximum likelihood technique to determine the mass distribution of its members, including single stars and both components of binary systems. This method allows me to determine not just the fraction of systems which are binary, but also the typical degree of correlation between the masses of their components. I also examine the spatial distribution of the cluster members. The issue of mass segregation is also addressed, introducing a new method for quantifying it.After quantifying many different properties of the cluster, N-body simulations are used to find the initial state that evolves to most closely match the current cluster. Although a few similar studies have been done in the past, I use a far larger breadth of parameters to compare with the actual data than any previous work. This results in a fairly confident determination of the properties of very young clusters, which any theory of cluster formation will be required to explain. How the cluster evolves from that initial state to the current day and beyond is also examined in detail.These techniques are used to examine two relatively close and well-known examples of open clusters: the Pleiades and the Alpha Persei cluster. In the case of the former, I find in particular that the overall binary fraction is as high as 76%, significantly higher than the accepted field-star result. The primary and secondary masses within binaries are found to be correlated, in the sense that their ratios are closer to unity than under the hypothesis of random pairing. I also find unambiguous evidence of mass segregation within the cluster.Building on these results, I find the original cluster, newly stripped of gas, to have already had a virial radius of 4 pc. This configuration was larger than most observed, embedded clusters. Over time, the cluster expanded further and the central surface density fell by about a factor of two. I attribute both effects to the liberation of energy from tightening binaries of short period. Indeed, the original binary fraction was close to unity. The ancient Pleiades also had significant mass segregation, which persists in the cluster today. In the future, the central density of the Pleiades will continue to fall. For the first few hundred Myr, the cluster as a whole will expand because of dynamical heating by binaries. The expansion process is aided by mass loss through stellar evolution, which weakens the system's gravitational binding. At later times, the Galactic tidal field begins to heavily deplete the cluster mass. Barring destruction by close passage of a giant molecular cloud, the density falloff will continue for as long as 1 Gyr, by which time most of the cluster mass will have been tidally stripped away by the Galactic field.This same analysis is also applied to Alpha Persei. Here I fist compile the most complete photometric catalog of the system to date. The stellar mass function is found to be weighted more heavily toward higher-mass stars than in the Pleiades. Also in contrast with the Pleiades, I find there to be essentially no mass segregation in the cluster, either today or in its initial state. The binary fraction, however, is found to be quite similar between the two clusters, as high as 70% in Alpha Persei. Once more the initial state is found to be quite large compared to embedded systems. The results of these two clusters together argue strongly the young clusters experience a period of significant expansion associated with the loss of their natal gas. Over time, Alpha Persei will globally expanded as a result of the Galactic tidal field. Dynamical heating by binaries, along with mass loss through stellar evolution, will also inflate the cluster into the future. I predict that Alpha Persei will completely dissolve within the next 300 Myr.Utilizing a series of N-body simulations, I go on to argue that gravitationally bound stellar clusters of modest population evolve very differently from the picture presented by classical dynamical relaxation theory. The system's most massive stars rapidly sink towards the center and form binary systems. These binaries efficiently heat the cluster, reversing any incipient core contraction and driving a subsequent phase of global expansion. Most previous theoretical studies demonstrating deep and persistent dynamical relaxation have either conflated the process with mass segregation, ignored three-body interactions, or else adopted the artificial assumption that all cluster members are single stars of identical mass. In such a uniform-mass cluster, binary formation is greatly delayed, as we confirm here both numerically and analytically. The relative duration of core contraction and global expansion is effected by stellar evolution, which causes the most massive stars to die out before they form binaries. In clusters of higher N, the epoch of dynamical relaxation lasts for progressively longer periods. By extrapolating our results to much larger populations we can understand, at least qualitatively, why some globular clusters reach the point of true core collapse.
Book ChapterDOI
01 May 2005
TL;DR: In this paper, the authors used high-resolution near-infrared Keck/NIRSPEC echelle spectroscopy to measure the stellar velocity dispersions in a nuclear starburst in M82.
Abstract: The nuclear starburst in M82 is host to over 20 infrared-bright, dense, young super star clusters (SSCs). We use high-resolution near-infrared Keck/NIRSPEC echelle spectroscopy to measure the stellar velocity dispersions. The SSCs are resolved in Hubble Space Telescope images, from which we measure half-light radii and integrated luminosities. We calculate virial masses for the SSCs, and compare the observed light-to-mass ratios to population synthesis models to constrain the initial mass function. There are apparent variations of the IMF within this single starburst galaxy. We present evidence for mass segregation despite the young ages, and discuss implications for the interpretation of the IMF.

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