------------------------------------------------------------------------
 dale_giant_colllision08.tex MNRAS, 2008, in press
From: "James Edward Dale" <jim@ig.cas.cz>
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%astro-ph/0811.3111
\documentclass[useAMS,usenatbib]{mn2e}
\bibliographystyle{mn2e}
\usepackage{graphicx}
\usepackage{latexsym,amsmath,amssymb}
\usepackage{subfigure}

\title{Red giant stellar collisions in the Galactic Centre}

\author[James E. Dale, Melvyn B. Davies, Ross P. Church, Marc
Freitag]{James. E. Dale$^{1}$\thanks{E-mail: jim@astro.lu.se (JED)},
Melvyn B. Davies$^{1}$, Ross P. Church$^{1,2}$, Marc Freitag$^{3}$\\
$^{1}$Lund Observatory, Box 43, SE--221 00, Lund, Sweden\\
$^{2}$School of Mathematical Sciences, Monash University, Victoria 3800,
Australia\\
$^{3}$Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK}


\begin{document}

\pagerange{\pageref{firstpage}--\pageref{lastpage}} \pubyear{2006}

\maketitle

\label{firstpage}

\def\solmas{{M$_\odot$}}
\def\solm{{M_\odot}}
\def\mnras{MNRAS}
\def\apj{ApJ}
\def\aap{A\&A}
\def\aj{AJ}
\def\apjl{ApJL}
\def\apjs{ApJS}
\def\bain{BAIN}
\def\pasp{PASP}
\def\araa{ARA\&A}
\def\physrep{Phys. Rep.}
\def\aaps{AAPS}
\def\ga{\sim}

\begin{abstract}
We show that collisions with stellar--mass black holes can partially
explain the absence of bright giant stars in the Galactic Centre, first
noted by \cite{1996ApJ...472..153G}. We show that the missing objects are
low--mass giants and AGB stars in the range $1-3$\,M$_{\odot}$. Using
detailed stellar evolution calculations, we find that to prevent these
objects from evolving to become visible in the depleted K bands, we
require that they suffer collisions on the red giant branch, and we
calculate the fractional envelope mass losses required. Using a
combination of Smoothed Particle Hydrodynamic calculations, restricted
three--body analysis and Monte Carlo simulations, we compute the expected
collision rates between giants and black holes, and between giants and
main--sequence stars in the Galactic Centre. We show that collisions can
plausibly explain the missing giants in the $10.5<K<12$ band. However,
depleting  the brighter ($K<10.5$) objects out to the required radius
would require a large population of black hole impactors which would in
turn deplete the $10.5<K<12$ giants in a region much larger than is
observed. We conclude that collisions with stellar--mass black holes
cannot account for the depletion of the very brightest giants, and we use
our results to place limits on the population of stellar--mass black holes
in the Galactic Centre.
\end{abstract}

\end{document}