------------------------------------------------------------------------
From: ZADEH@OSSENU.ASTRO.NWU.EDU
Date: Wed, 23 Sep 1998 10:13:40 -0500 (CDT)
To: hfalcke@mpifr-bonn.mpg.de
Subject: RE: conference

%astro-ph/9809279
1720
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\received{00  1998}
\accepted{00 1998}
%\journalid{337}{15 January 1989}
%\articleid{11}{14}
\centerline{Submitted to the Editor of the ApJ 
 on June 30, 1998}
\slugcomment{Re-submitted on August 15, 1998}
\lefthead{Yusef-Zadeh, Roberts \& Goss}
\righthead{OH (1720 MHz) Observations}

\def\ddeg   {\hbox{$.\!\!^\circ$}}              % Degrees over dot
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\def\msol   {\hbox{$M_\odot$}}                  % Solar mass
\def\i      {\hbox{\it I}}                      % italic I
\def\v      {\hbox{\it V}}                      % italic V
\def\dasec  {\hbox{$.\!\!^{\prime\prime}$}}     % Arcseconds over dot
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\def\dasec  {\hbox{$.\!\!^{\prime\prime}$}}     % Arcseconds over dot
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\def\etal   {{\it et al. }}                     % et al.

\begin{document}
\title{High-resolution Observations of OH(1720 MHz) Masers\\
 Toward the Galactic Center}


\author{F. Yusef-Zadeh}
\affil{Department of Physics and Astronomy, Northwestern University, 
Evanston, Il. 60208 (zadeh@nwu.edu)}

\author{D. A. Roberts}
\affil{NCSA, 405 N. Mathews Ave, Urbana, IL 61801
 (dougr@ncsa.uiuc.edu)}

\author{W. M. Goss and  D.A. Frail}
\affil{National Radio Astronomy Observatory, P.O. Box 0, 
Socorro, New Mexico 87801 (mgoss@aoc.nrao.edu), (dfrail@aoc.nrao.edu)}

\author{A. J. Green}
\affil{University of Sydney, School of Physics, A28, Sydney, NSW 2006
Australia (agreen@physics.usyd.edu.au)}

\begin{abstract}

High-resolution VLA observations of 1720 MHz OH maser emission from
Sgr A East and the circumnuclear disk with spatial and spectral
resolutions of $\approx$ 2\dasec5 $\times$ 1\dasec3 and 0.27 \kms\
are reported. This follow-up observational study focuses on the recent
discovery of a number of such OH maser features and their intense
circularly polarized maser lines detected toward these Galactic center
sources.  The 1720 MHz maser line of OH arises from collisionally
excited gas behind a C-type shock and is an important diagnostic of
the interaction process that may occur between molecular clouds and
associated X-ray emitting shell-type supernova remnants.  The present
observations have confirmed that the observed Stokes $V$ signal is due
to Zeeman splitting and that the OH masers are angularly broadened by
the scattering medium toward the Galactic center.  The scale length of
the magnetic field fluctuations in the scattering medium toward the
Galactic center is estimated to be greater than 0.1-0.2 pc using the
correlation of the position angles of the scatter-broadened maser
spots.  In addition, the kinematics of the maser spots associated with
Sgr A East are used to place a 5 pc displacement between this extended
radio structure and the Galactic center.

\end{abstract}
\end{document}

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