The effect of stellar-mass black holes on the structural evolution of massive star clusters

We present the results of realistic N-body modelling of massive star clusters in the Magellanic Clouds, aimed at investigating a dynamical origin for the radius-age trend observed in these systems. We find that stellar-mass black holes, formed in the supernova explosions of the most massive cluster stars, can constitute a dynamically important population. If a significant ensemble is retained (here we assume complete retention), these objects rapidly form a dense core where interactions are common, resulting in the scattering of black holes into the cluster halo, and the ejection of black holes from the cluster. These two processes heat the stellar component, resulting in prolonged core expansion of a magnitude matching the observations. Significant core evolution is also observed in Magellanic Cloud clusters at early times. We find that this does not result from the action of black holes, but can be reproduced by the effects of mass-loss due to rapid stellar evolution in a primordially mass-segregated cluster. (Less)

[1]  P. Hut,et al.  Gravitational N-body Simulations , 2008, 0806.3950.

[2]  N. R. Tanvir,et al.  ACS Photometry of Extended, Luminous Globular Clusters in the Outskirts of M31 , 2006, astro-ph/0611257.

[3]  I. Bonnell,et al.  Star formation through gravitational collapse and competitive accretion , 2006, astro-ph/0604615.

[4]  W. Lewin,et al.  Compact stellar X-ray sources , 2006 .

[5]  R. P. van der Marel,et al.  Resolved Massive Star Clusters in the Milky Way and Its Satellites: Brightness Profiles and a Catalog of Fundamental Parameters , 2005, astro-ph/0605132.

[6]  F. Timmes,et al.  Understanding Compact Object Formation and Natal Kicks. I. Calculation Methods and the Case of GRO J1655–40 , 2004, astro-ph/0411423.

[7]  A. Mackey,et al.  Comparing the properties of local globular cluster systems: implications for the formation of the Galactic halo , 2004, astro-ph/0408404.

[8]  D. Merritt,et al.  Core Formation by a Population of Massive Remnants , 2004, astro-ph/0403331.

[9]  T. J. Dupuy,et al.  Cluster Mass Functions in the Large and Small Magellanic Clouds: Fading and Size-of-Sample Effects , 2003, astro-ph/0306528.

[10]  Ny,et al.  Core radius evolution of star clusters , 2003, astro-ph/0304522.

[11]  Cambridge,et al.  Surface brightness profiles and structural parameters for 53 rich stellar clusters in the Large Magellanic Cloud , 2002, astro-ph/0209031.

[12]  C. Tout,et al.  Evolution of binary stars and the effect of tides on binary populations , 2002, astro-ph/0201220.

[13]  U. Cambridge,et al.  Mass segregation in young compact star clusters in the Large Magellanic Cloud — II. Mass functions , 2001, astro-ph/0111312.

[14]  P. Kroupa.  On the variation of the initial mass function , 2000, astro-ph/0009005.

[15]  C. Tout,et al.  Comprehensive analytic formulae for stellar evolution as a function of mass and metallicity , 2000, astro-ph/0001295.

[16]  C. Jager.  The yellow hypergiants , 1998 .

[17]  Jeremiah P. Ostriker,et al.  Dynamical Evolution of Globular Clusters , 1996 .

[18]  Pierre Bergeron,et al.  PHOTOMETRIC CALIBRATION OF HYDROGEN- AND HELIUM-RICH WHITE DWARF MODELS , 1995 .

[19]  Steinn Sigurdsson,et al.  Primordial black holes in globular clusters , 1993, Nature.

[20]  Piet Hut,et al.  Stellar black holes in globular clusters , 1993, Nature.

[21]  A. Renzini,et al.  The Stellar Populations of Galaxies , 1992 .

[22]  Tod R. Lauer,et al.  Core expansion in young star clusters in the Large Magellanic Cloud , 1989 .

[23]  S. M. Fall,et al.  The Structure of Young Star Clusters in the Large Magellanic Cloud , 1987 .