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%http://www.astro.columbia.edu/~herrnstein/NH3/paper/
%astro-ph/0409271
\documentclass{aastex}
\usepackage{emulateapj5}
\usepackage{natbib}

% general newcommandsplot
\newcommand{\3}{$_3$}

\begin{document}

\title{The Nature of the Molecular Environment\\ within 5~pc of the
Galactic Center}
 
\author{
Robeson M. Herrnstein\altaffilmark{1} and

\altaffiltext{1}{Department of Astronomy, Columbia University, 550 West 120th Street, Mail Code 5246, New York, NY 10027, herrnstein@astro.columbia.edu}
\altaffiltext{1}{Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, \\pho@cfa.harvard.edu}

\begin{abstract}
We present a detailed study of molecular gas in the central 10~pc of
the Galaxy through spectral line observations of four rotation
inversion transitions of NH\3 made with the Very Large Array.  Updated
line widths and NH\3(1,1) opacities are presented, and temperatures,
column densities, and masses are derived for the major molecular
features.  We examine the impact of Sgr A East on molecular material
at the Galactic center and find that there is no evidence that the
expansion of this shell has moved a significant amount of the 50
km~s$^{-1}$ giant molecular cloud.  The western streamer, however,
shows strong indications that it is composed of material swept-up by
the expansion of Sgr A East.  Using the mass and kinematics of the
western streamer, we calculate an energy of
$E_{SN}=(2-9)\times10^{51}$~ergs for the progenitor explosion and
conclude that Sgr A East was most likely produced by a single
supernova.  The temperature structure of molecular gas in the central
$\sim20$~pc is also analyzed in detail.  We find that molecular gas
has a ``two-temperature'' structure similar to that measured by
Huttemeister et al. (1993a) on larger scales.  The largest observed
line ratios, however, cannot be understood in terms of a
two-temperature model, and most likely result from absorption of
NH\3(3,3) emission by cool surface layers of clouds.  By comparing the
observed NH\3 (6,6)-to-(3,3) line ratios, we disentangle three
distinct molecular features within a projected distance of 2~pc from
Sgr~A*.  Gas associated with the highest line ratios shows kinematic
signatures of both rotation and expansion.  The southern streamer
shows no significant velocity gradients and does not appear to be
directly associated with either the circumnuclear disk or the nucleus.
The paper concludes with a discussion of the line-of-sight arrangement
of the main features in the central 10~pc.
\end{abstract}

\end{document}