Topic
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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TL;DR: In this article, the authors present a Spitzer-based census of the IC 348 nebula and embedded star cluster and show that the current cluster configuration is the result of dynamical evolution and its primordial structure has been erased.
Abstract: We present a Spitzer based census of the IC 348 nebula and embedded star cluster. Our Spitzer census supplemented by ground based spectra has added 42 class II T-Tauri sources to the cluster membership and identified ~20 class 0/I protostars. The population of IC 348 likely exceeds 400 sources after accounting statistically for unidentified diskless members. Our Spitzer census of IC 348 reveals a population of protostars that is anti-correlated spatially with the T-Tauri members, which comprise the centrally condensed cluster around a B star. The protostars are instead found mostly at the cluster periphery about 1 pc from the B star and spread out along a filamentary ridge. We find that the star formation rate in this protostellar ridge is consistent with that rate which built the exposed cluster while the presence of fifteen cold, starless, millimeter cores intermingled with this protostellar population indicates that the IC 348 nebula has yet to finish forming stars. We show that the IC 348 cluster is of order 3-5 crossing times old, and, as evidenced by its smooth radial profile and confirmed mass segregation, is likely relaxed. While it seems apparent that the current cluster configuration is the result of dynamical evolution and its primordial structure has been erased, our findings support a model where embedded clusters are built up from numerous smaller sub-clusters. Finally, the results of our Spitzer census indicate that the supposition that star formation must progress rapidly in a dark cloud should not preclude these observations that show it can be relatively long lived.
6 citations
INAF1
TL;DR: In the last few years, X-ray observational studies of young star clusters have advanced significantly, mainly thanks to the great capabilities of current Xray observatories such as Chandra and XMM/Newton as discussed by the authors.
Abstract: In the last few years, X-ray observational studies of young star clusters have advanced significantly, mainly thanks to the great capabilities of current X-ray observatories such as Chandra and XMM/Newton. In addition to enabling a detailed study of coronae of individual bright stars, high-spatial-resolution X-ray observations of many young clusters and star-forming regions, even massive and distant ones, have led to the detection of large populations of X-ray-bright members, often down to subsolar masses, and despite strong absorption. The peculiar ability of X-ray emission to select young, low-mass cluster stars against a crowded Galactic-plane field-star background has permitted better studies of global cluster properties, with respect to optical/infrared studies alone, including of cluster initial mass functions (across wide mass ranges), star-formation histories (with indication of age spreads—or even sequences—in many clusters) and morphologies (various degrees of symmetry and dynamical relaxation), sometimes with evidence of mass segregation. Also, the complementary availability of X-ray and optical/infrared data has enabled to place constraints on lifetimes and depletion mechanisms of pre-main-sequence circumstellar disks.
6 citations
TL;DR: The DBSCAN algorithm has been used for the first time to make the membership determination of the open clusters NGC 6791 and M 67 and it is demonstrated that it has some advantages superior to the conventional kinematic method.
6 citations
TL;DR: In this article , the authors investigated the relationship between the global properties of star clusters and their double black hole (DBH) populations and concluded that cluster metallicity plays the most significant role in determining the lifespan of a cluster, while the initial half-mass radius is dominant in setting the rate of BH exchange interactions in central cluster regions.
Abstract: We investigate the relationship between the global properties of star clusters and their double black hole (DBH) populations. We use the code NBODY6 to evolve a suite of star cluster models with an initial mass of O( 10 4 ) M (cid:12) and varying initial parameters. We conclude that cluster metallicity plays the most significant role in determining the lifespan of a cluster, while the initial half-mass radius is dominant in setting the rate of BH exchange interactions in the central cluster regions. We find that the mass of interacting BHs, rather than how frequently their interactions with other BHs occur, is more crucial in the thermal expansion and eventual evaporation of the cluster. We formulate a novel approach to easily quantify the degree of BH-BH dynamical activity in each model. We report 12 in-cluster and three out-of-cluster (after ejection from the cluster) DBH mergers, of different types (inspiral, eccentric, hierarchical) across the ten 𝑁 -body models presented. Our DBH merger efficiency is 3–4 × 10 − 5 mergers per M (cid:12) . We note the cluster initial density plays the most crucial role in determining the number of DBH mergers, with the potential presence of a transitional density point (between 1.2-3.8 × 10 3 M (cid:12) /pc 3 ) below which the number of in-cluster mergers increases with cluster density and above which the increased stellar density acts to prevent in-cluster BH mergers. The importance of the history of dynamical interactions within the cluster in setting up the pathways to ejected DBH mergers is also discussed.
6 citations
Posted Content•
TL;DR: In this paper, the dynamical evolution of the young star cluster Arches and its dependence on the assumed initial stellar mass function (IMF) was studied and the possibility of a collisional runaway was investigated.
Abstract: We study the dynamical evolution of the young star cluster Arches and its dependence on the assumed initial stellar mass function (IMF). We perform many direct N-body simulations with various initial conditions and two different choices of IMFs. One is a standard Kroupa IMF without any mass segregation. The other is a radially dependent IMF, as presently observed in the Arches. We find that it is unlikely for the Arches to have attained the observed degree of mass segregation at its current age starting from a standard non-segregated Kroupa IMF. We also study the possibility of a collisional runaway developing in the first � 2 −3Myr of dynamical evolution. We find that the evolution of this cluster is dramatically different depending on the choice of IMF: if a primordially mass segregated IMF is chosen, a collisional runaway should always occur between 2−3Myr for a broad range of initial concentrations. In contrast, for a standard Kroupa IMF no collisional runaway is predicted. We argue that if Arches was created with a mass segregated IMF similar to what is observed today then at the current cluster age a very unusual, high-mass star should be created. However, whether a collisional runaway leads to the formation of an intermediate-mass black hole (IMBH) depends strongly on the mass loss rate via winds from massive stars. Growth of stellar mass through collisions can be quenched by strong wind mass loss. In that case, the inter-cluster as well as intra-cluster medium are expected to have a significant Helium enrichment which may be observed via Helium recombination lines. The excess amount of gas lost in winds may also be observed via X-ray observations as diffused X-ray sources. Subject headings: methods: N-body simulations, methods: numerical, globular clusters: individual (Arches), stellar dynamics
6 citations