Dynamics of stellar black holes in young star clusters with different metallicities - II. Black hole-black hole binaries
Abstract
In this paper, we study the formation and dynamical evolution of black hole-black hole (BH-BH) binaries in young star clusters (YSCs), by means of N-body simulations. The simulations include metallicity-dependent recipes for stellar evolution and stellar winds, and have been run for three different metallicities (Z = 0.01, 0.1 and 1 Z⊙). Following recent theoretical models of wind mass-loss and core-collapse supernovae, we assume that the mass of the stellar remnants depends on the metallicity of the progenitor stars. We find that BH-BH binaries form efficiently because of dynamical exchanges: in our simulations, we find about 10 times more BH-BH binaries than double neutron star binaries. The simulated BH-BH binaries form earlier in metal-poor YSCs, which host more massive black holes (BHs) than in metal-rich YSCs. The simulated BH-BH binaries have very large chirp masses (up to 80 M⊙), because the BH mass is assumed to depend on metallicity, and because BHs can grow in mass due to the merger with stars. The simulated BH-BH binaries span a wide range of orbital periods (10-3-107 yr), and only a small fraction of them (0.3 per cent) is expected to merge within a Hubble time. We discuss the estimated merger rate from our simulations and the implications for Advanced VIRGO and LIGO.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2014
- DOI:
- 10.1093/mnras/stu824
- arXiv:
- arXiv:1404.7147
- Bibcode:
- 2014MNRAS.441.3703Z
- Keywords:
-
- black hole physics;
- gravitational waves;
- methods: numerical;
- binaries: general;
- galaxies: star clusters: general;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics;
- General Relativity and Quantum Cosmology
- E-Print:
- 17 pages, 12 figures, 4 tables, MNRAS, in press