SCYON Abstract

Received on: 24 07 2018

The long-term evolution of star clusters formed with a centrally-peaked star-formation-efficiency profile

Authors:B. Shukirgaliyev 1,2, G. Parmentier 1, A. Just 1, P. Berczik 3,4
Affiliations:(1) Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Heidelberg, Germany; (2) Fesenkov Astrophysical Institute, Almaty, Kazakhstan; (3) National Astronomical Observatories of China and Key Laboratory for Computational Astrophysics, Chinese Academy of Sciences, Chaoyang District, Beijing, China; (4) Main Astronomical Observatory, National Academy of Sciences of Ukraine, Kyiv, Ukraine
Accepted by: Astrophysical Journal

We have studied the long-term evolution of star clusters of the solar neighborhood, starting from their birth in gaseous clumps until their complete dissolution in the Galactic tidal field. We have combined the "local-density-driven cluster formation model" of Parmentier & Pfalzner (2013) with direct N-body simulations of clusters following instantaneous gas expulsion. We have studied the relation between cluster dissolution time, $t_{dis}$, and cluster "initial" mass, $M_{init}$, defined as the cluster {mass at the end of the dynamical response to gas expulsion (i.e. violent relaxation), when the cluster age is 20-30 Myr}. We consider the "initial" mass to be consistent with other works which neglect violent relaxation. The model clusters formed with a high star formation efficiency (SFE - i.e. gas mass fraction converted into stars) follow a tight mass-dependent relation, in agreement with previous theoretical studies. However, the low-SFE models present a large scatter in both the "initial" mass and the dissolution time, and a shallower mass-dependent relation than high-SFE clusters. Both groups differ in their structural properties on the average. Combining two populations of clusters, high- and low-SFE ones, with domination of the latter, yields a cluster dissolution time for the solar neighborhood in agreement with that inferred from observations, without any additional destructive processes such as giant molecular cloud encounters. An apparent mass-independent relation may emerge for our low-SFE clusters when we neglect low-mass clusters (as expected for extra-galactic observations), although more simulations are needed to investigate this aspect.

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