期刊
ASTROPHYSICAL JOURNAL
卷 744, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/744/1/74
关键词
black hole physics; galaxies: nuclei
资金
- National Science Foundation [AST 08-07910, 08-21141]
- National Aeronautics and Space Administration [NNX-07AH15G]
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [0807910] Funding Source: National Science Foundation
We simulate mergers between galaxies containing collisionally relaxed nuclei around massive black holes (MBHs). Our galaxies contain four mass groups, representative of old stellar populations; a primary goal is to understand the distribution of stellar-mass black holes (BHs) after the merger. Mergers are followed using direct-summation N-body simulations, assuming a mass ratio of 1: 3 and two different orbits. Evolution of the binary MBH is followed until its separation has shrunk by a factor of 20 below the hard-binary separation. During the galaxy merger, large cores are carved out in the stellar distribution, with radii several times the influence radius of the massive binary. Much of the pre-existing mass segregation is erased during this phase. We follow the evolution of the merged galaxies for approximately three central relaxation times after coalescence of the massive binary; both standard and top-heavy mass functions are considered. The cores that were formed in the stellar distribution persist, and the distribution of the stellar-mass BHs evolves against this essentially fixed background. Even after one central relaxation time, these models look very different from the relaxed, multi-mass models that are often assumed to describe the distribution of stars and stellar remnants near a massive BH. While the stellar BHs do form a cusp on roughly a relaxation timescale, the BH density can be much smaller than in those models. We discuss the implications of our results for the extreme-mass-ratio inspiral problem and for the existence of Bahcall-Wolf cusps.
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