Volume 526, February 2011
|Number of page(s)||6|
|Section||Cosmology (including clusters of galaxies)|
|Published online||14 December 2010|
Black holes and galactic density cusps
From black hole to bulge
Instituto de Física Teórica UAM/CSIC, Facultad de Ciencias, C-XI,
Universidad Autónoma de Madrid Cantoblanco,
2 Queen’s University, Kingston, Ontario, Canada
3 Faculty of Science, University of Ontario Institute of Technology, Oshawa, L1H 7K4 Ontario, Canada
Accepted: 26 October 2010
Aims. In this paper we continue our study of density cusps that may contain central black holes.
Methods. Our previous thus attempts to use distribution functions with a memory of self-similar relaxation apply mainly in restricted regions of the global system. We are forced to consider related distribution functions that are steady but not self-similar.
Results. One remarkably simple distribution function that has a filled loss cone describes a bulge that transits from a near black hole domain to an outer “zero flux” regime where ρ ∝ r−7/4. The transition passes from an initial inverse square profile through a region having a 1/r density profile. The structure is likely to be developed at an early stage in the growth of a galaxy. A central black hole is shown to grow exponentially in this background with an e-folding time of a few million years.
Conclusions. We derive our results from first principles, using only the angular momentum integral in spherical symmetry. The initial relaxation probably requires bar instabilities and clump-clump interactions.
Key words: cosmology: theory / dark matter / galaxies: halos / galaxies: nuclei / black hole physics / gravitation
© ESO, 2010
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