Ejection of hypervelocity stars from the Galactic Centre by intermediate-mass black holes

Baumgardt, H., Gualandris, A. and Zwart, S. Portegies (2006) Ejection of hypervelocity stars from the Galactic Centre by intermediate-mass black holes. Monthly Notices of the Royal Astronomical Society, 372 1: 174-182. doi:10.1111/j.1365-2966.2006.10818.x


Author Baumgardt, H.
Gualandris, A.
Zwart, S. Portegies
Title Ejection of hypervelocity stars from the Galactic Centre by intermediate-mass black holes
Journal name Monthly Notices of the Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711
1365-2966
Publication date 2006-10-01
Year available 2006
Sub-type Article (original research)
DOI 10.1111/j.1365-2966.2006.10818.x
Open Access Status DOI
Volume 372
Issue 1
Start page 174
End page 182
Total pages 9
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Abstract We have performed N-body simulations of the formation of hypervelocity stars (HVS) in the centre of the Milky Way due to inspiralling intermediate-mass black holes (IMBHs). We considered IMBHs of different masses, all starting from circular orbits at an initial distance of 0.1 pc. We find that the IMBHs sink to the centre of the Galaxy due to dynamical friction, where they deplete the central cusp of stars. Some of these stars become HVS and are ejected with velocities sufficiently high to escape the Galaxy. Since the HVS carry with them information about their origin, in particular in the moment of ejection, the velocity distribution and the direction in which they escape the Galaxy, detecting a population of HVS will provide insight in the ejection processes and could therefore provide indirect evidence for the existence of IMBHs.
Formatted abstract
We have performed N-body simulations of the formation of hypervelocity stars (HVS) in the centre of the Milky Way due to inspiralling intermediate-mass black holes (IMBHs). We considered IMBHs of different masses, all starting from circular orbits at an initial distance of 0.1 pc. We find that the IMBHs sink to the centre of the Galaxy due to dynamical friction, where they deplete the central cusp of stars. Some of these stars become HVS and are ejected with velocities sufficiently high to escape the Galaxy. Since the HVS carry with them information about their origin, in particular in the moment of ejection, the velocity distribution and the direction in which they escape the Galaxy, detecting a population of HVS will provide insight in the ejection processes and could therefore provide indirect evidence for the existence of IMBHs. Our simulations show that HVS are generated in short bursts which last only a few Myr until the IMBH is swallowed by the supermassive black hole (SMBH). HVS are ejected almost isotropically, which makes IMBH-induced ejections hard to distinguish from ejections due to encounters of stellar binaries with a SMBH. After the HVS have reached the galactic halo, their escape velocities correlate with the distance from the Galactic Centre in the sense that the fastest HVS can be found furthest away from the centre. The velocity distribution of HVS generated by inspiralling IMBHs is also nearly independent of the mass of the IMBH and can be quite distinct from one generated by binary encounters. Finally, our simulations show that the presence of an IMBH in the Galactic Centre changes the stellar density distribution inside r < 0.02 pc into a core profile, which takes at least 100 Myr to replenish.
Keyword Black hole physics
Stellar dynamics
Globular clusters : general
Clusters
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
ERA 2012 Admin Only
 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 81 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 76 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Tue, 24 Jan 2012, 21:52:15 EST by System User on behalf of Physics