------------------------------------------------------------------------
 hvspaper.tex ApJ, submitted
To: gcnews@aoc.nrao.edu
MIME-Version: 1.0
Content-Type: TEXT/plain; charset=us-ascii
Content-MD5: 5LSc9rKwAHIgEP5kJoVULQ==
X-Mailer: dtmail 1.3.0 @(#)CDE Version 1.5.7 SunOS 5.9 sun4u sparc 
X-MailScanner-Information: Please contact the postmaster@aoc.nrao.edu for more information
X-MailScanner: Found to be clean
X-MailScanner-SpamCheck: not spam, SpamAssassin (not cached, score=0,
	required 5, autolearn=disabled)
X-MailScanner-From: kenyon@cfa.harvard.edu
X-Spam-Status: No

%astro-ph/0801.3479

%\documentclass{aastex}
\documentclass[12pt,preprint]{aastex}
%\documentclass{emulateapj}
%\documentclass{article}
%\usepackage{emulateapj}
\usepackage{epsf}

\usepackage{graphicx}
\usepackage{natbib}
\bibliographystyle{apj}

\def\new#1{\bf #1 \rm}
\def\old#1{}
\def\newmath#1{#1}
\def\oldmath#1{}

\def\abin{a_{\rm bin}}
\def\rclose{r_{\rm close}}
\def\acore{a_{\rm c}}
\def\dmin{D_{\rm min}}
\def\ma{m_1}
\def\mb{m_2}
\def\va{v_1}
\def\vb{v_2}
\def\vej{v_{\rm ej}}
\def\veja{v_{\rm ej,1}}
\def\vejb{v_{\rm ej,2}}
\def\tlife{t_{\rm ms}}
\def\reff{r_{\rm eff}}
\def\Mbh{M_\bullet}

\def\Msolar{M$_\odot$}
\def\msun{M$_\odot$}
\def\lsun{L$_\odot$}
\def\mathMsolar{{\rm M}_\odot}
\def\facR{f_R}
\def\sgr{Sgr~A$^\ast$}
\def\GC{Galactic Center}
\def\kms{km~s$^{-1}$}
\def\AU{{\sc au}}

\begin{document}

\title{Hypervelocity Stars: From the Galactic Center to the Halo}

\author{Scott J. Kenyon}
\affil{Smithsonian Astrophysical Observatory,
\\ 60 Garden St., Cambridge, MA 02138}
\email{skenyon@cfa.harvard.edu}

\author{Benjamin C. Bromley}
\affil{Department of Physics, University of Utah,
\\ 115 S 1400 E, Rm 201, Salt Lake City, UT 84112}
\email{bromley@physics.utah.edu}

\author{Margaret J. Geller}
\affil{Smithsonian Astrophysical Observatory,
\\ 60 Garden St., Cambridge, MA 02138}
\email{mgeller@cfa.harvard.edu}

\author{Warren R. Brown}
\affil{Smithsonian Astrophysical Observatory,
\\ 60 Garden St., Cambridge, MA 02138}
\email{wbrown@cfa.harvard.edu}

\begin{abstract}
Hypervelocity stars (HVS) traverse the Galaxy from the central black hole to
the outer halo. We show that the Galactic potential within 200 pc acts as
a high pass filter preventing low velocity HVS from reaching the halo. To
trace the orbits of HVS throughout the Galaxy, we construct two forms of the
potential which reasonably represent the observations in the range 5--10$^5$
pc, a simple spherically symmetric model and a bulge-disk-halo model. We use
the Hills mechanism (disruption of binaries by the tidal field of the central
black hole) to inject HVS into the Galaxy and compute the observable spatial
and velocity distributions of HVS with masses in the range 0.6--4 M$_\odot$.
These distributions reflect the mass function in the \GC, properties of
binaries in the \GC, and aspects of stellar evolution and the injection
mechanism. For 0.6--4 \msun\ main sequence stars, the fraction of unbound
HVS and the asymmetry of the velocity distribution for their bound
counterparts increases with stellar mass. The density profiles for
unbound HVS decline with distance from the \GC\ approximately as
$r^{-2}$ (but are steeper for the most massive stars which evolve off
the main sequence during their travel time from the \GC); the density
profiles for the bound ejecta decline with distance approximately as
$r^{-3}$. In a survey with limiting magnitude $V \lesssim$ 23, the
detectability of HVS (unbound or bound) increases with stellar mass.

\end{abstract}

\end{document}