How fast is mass segregation happening in hierarchically formed embedded star clusters?

Domínguez, Raimundo; Fellhauer, M.; Blaña, M.; Farias, J. P.; Dabringhausen, J.

doi:10.1093/mnras/stx1883

Cited by 23 publications

(23 citation statements)

References 57 publications

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“…Studies of clusters' formation and very early evolution have shown that clusters can emerge from these evolutionary phases with dynamical properties characterized by mass segregation, internal rotation, and radial anisotropy in the velocity distribution; the detailed role of different dynamical processes acting during these phases and the variety of different dynamical paths resulting in these dynamical properties are still matter of intense investigation (see e.g. Goodwin & Whitworth 2004, McMillan et al 2007, Allison et al 2009, 2010, Moeckel & Bonnell 2009, Fujii et al 2012, Fujii & Portegies Zwart 2016, Vesperini et al 2014, Parker et al 2016, Domínguez et al 2017, Mapelli 2017, Banerjee & Kroupa 2014, 2017, Sills et al 2018, Daffern-Powell & Parker 2020, Ballone et al 2020, Ballone et al 2021.…”

Section: Introductionmentioning

confidence: 99%

Early dynamics and violent relaxation of multimass rotating star clusters

Livernois

Vesperini

Tiongco

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present the results of a study aimed at exploring, by means of N-body simulations, the evolution of rotating multi-mass star clusters during the violent relaxation phase, in the presence of a weak external tidal field. We study the implications of the initial rotation and the presence of a mass spectrum for the violent relaxation dynamics and the final properties of the equilibria emerging at the end of this stage. Our simulations show a clear manifestation of the evolution towards spatial mass segregation and evolution towards energy equipartition during and at the end of the violent relaxation phase. We study the final rotational kinematics and show that massive stars tend to rotate more rapidly than low-mass stars around the axis of cluster rotation. Our analysis also reveals that during the violent relaxation phase, massive stars tend to preferentially segregate into orbits with angular momentum aligned with the cluster’s angular momentum, an effect previously found in the context of the long-term evolution of star clusters driven by two-body relaxation.

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Section: Introductionmentioning

confidence: 99%

Early dynamics and violent relaxation of multimass rotating star clusters

Livernois

Vesperini

Tiongco

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…For example, the value of the SFE, initial cluster radii, the time-scale of gas expulsion and the degree of primordial mass segregation are subject to ongoing research (e.g. Er et al 2013;Kuhn et al 2014;Banerjee & Kroupa 2015;Megeath et al 2016;Spera & Capuzzo-Dolcetta 2017;Domínguez et al 2017;Pfalzner 2019;Kuhn et al 2019;Dib & Henning 2019;Pang et al 2020). Some of the cluster initial conditions are interrelated: for example, embedded star clusters cannot form with sub-parsec scales and SFE close to 100% because they would not be able to expand to their observed sizes (Banerjee & Kroupa 2017).…”

Section: The Influence Of the Initial Conditions Of Star Clustersmentioning

confidence: 99%

Do the majority of stars form as gravitationally unbound?

Dinnbier,

Kroupa,

Anderson

2022

Preprint

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Context. Some of the youngest stars (age 10 Myr) are clustered, while many others are observed scattered throughout star forming regions or in complete isolation. It has been intensively debated whether the scattered or isolated stars originate in star clusters, or if they form truly isolated, which could help constrain the possibilities how massive stars are formed. Aims. We adopt the assumption that all stars form in gravitationally bound star clusters embedded in molecular cloud cores (Γ-1 model), which expel their natal gas early after their formation, and compare the fraction of stars found in clusters with observational data. Methods. The star clusters are modelled by the code nbody6, which includes binary stars, stellar and circumbinary evolution, gas expulsion, and the external gravitational field of their host galaxy. Results. We find that small changes in the assumptions in the current theoretical model estimating the fraction, Γ, of stars forming in embedded clusters have a large influence on the results, and we present a counterexample as an illustration. This calls into question theoretical arguments about Γ in embedded clusters, and it suggests that there is no firm theoretical ground for low Γ in galaxies with lower star formation rates (SFRs). Instead, the assumption that all stars form in embedded clusters is in agreement with observational data for the youngest stars (age 10 Myr). In the Γ-1 scenario, the observed fraction of the youngest stars in clusters increases with the SFR only weakly; the increase is caused by the presence of more massive clusters in galaxies with higher SFRs, which release fewer stars to the field in proportion to their mass. The Γ-1 model yields a higher fraction of stars in clusters for older stars (age between 10 Myr and 300 Myr) than what is observed. This discrepancy can be caused by initially less compact clusters and/or a slightly lower star formation efficiency than originally assumed in the Γ-1 model, or by interactions of the post gas expulsion revirialised open clusters with molecular clouds.

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“…Broadly, real star clusters are categorised into two types based on their structure: (i) Centrally condensed type star clusters, and (ii) Hierarchical-type clusters. The structure of a cluster is related to the underlying star formation mechanisms at work (Lada & Lada 2003;Gutermuth et al 2005;Dominguez et al 2017). Centrally-condensed type of clusters usually have a single prominent peak and show highly concentrated surface density distributions with relatively smooth radial profiles, whereas hierarchical-type clusters display evidence of clustering over a large area and contain multiple peaks.…”

Section: Simulated Clustersmentioning

confidence: 99%

Star cluster detection and characterization using generalized Parzen density estimation

Nambiar

Das

Vig

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Star cluster studies hold the key to understanding star formation, stellar evolution, and origin of galaxies. The detection and characterization of clusters depend on the underlying background density and the cluster richness. We examine the ability of the Parzen Density Estimation (a.k.a. Parzen Windows) method, which is a generalization of the well-known Star Count method, to detect clusters and measure their properties. We apply it on a range of simulated and real star fields, considering square and circular windows, with and without Gaussian kernel smoothing. Our method successfully identifies clusters and we suggest an optimal standard deviation of the Gaussian Parzen window for obtaining the best estimates of these parameters. Finally, we demonstrate that the Parzen Windows with Gaussian kernels are able to detect small clusters in regions of relatively high background density where the Star Count method fails.

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How fast is mass segregation happening in hierarchically formed embedded star clusters?

Cited by 23 publications

References 57 publications

Early dynamics and violent relaxation of multimass rotating star clusters

Early dynamics and violent relaxation of multimass rotating star clusters

Do the majority of stars form as gravitationally unbound?

Star cluster detection and characterization using generalized Parzen density estimation

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