Journal Article

Growing massive black holes in a Local Group environment: the central supermassive, slowly sinking and ejected populations

Miroslav Micic, Kelly Holley-Bockelmann and Steinn Sigurdsson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 2, pages 1127-1144
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18444.x
Growing massive black holes in a Local Group environment: the central supermassive, slowly sinking and ejected populations

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We explore the growth of ≤107 M black holes that reside at the centres of spiral and field dwarf galaxies in a Local Group type of environment. We use merger trees from a cosmological N-body simulation known as Via Lactea 2 (VL-2) as a framework to test two merger-driven semi-analytic recipes for black hole growth that include dynamical friction, tidal stripping and gravitational wave recoil in over 20 000 merger tree realizations. First, we apply a Fundamental Plane limited (FPL) model to the growth of Sgr A*, which drives the central black hole to a maximum mass limited by the black hole Fundamental Plane after every merger. Next, we present a new model that allows for low-level prolonged gas accretion (PGA) during the merger. We find that both models can generate an Sgr A* mass black hole. We predict a population of massive black holes in local field dwarf galaxies – if the VL-2 simulation is representative of the growth of the Local Group, we predict up to 35 massive black holes (≤106 M) in Local Group field dwarfs. We also predict that hundreds of ≤105 M black holes fail to merge, and instead populate the Milky Way halo, with the most massive of them at roughly the virial radius. In addition, we find that there may be hundreds of massive black holes ejected from their hosts into the nearby intergalactic medium due to gravitational wave recoil. We discuss how the black hole population in the Local Group field dwarfs may help to constrain the growth mechanism for Sgr A*.

Keywords: black hole physics; Galaxy: centre; galaxies: haloes; galaxies: high-redshift; Local Group

Journal Article.  14872 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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