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 odingc118abstr.tex A&A, in press
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%astro-ph/0803.1726

\documentclass{aa}

\usepackage{graphicx}
\usepackage{txfonts}
%\input{psfig}

%
\begin{document}

\title{Odin observations of the Galactic centre in the 118-GHz
band. Upper limit to the O$_{2}$\ abundance}

\subtitle{}

\author{Aa.\,Sandqvist\inst{1}
   \and B.\,Larsson\inst{1}
   \and \AA .\,Hjalmarson\inst{2}
   \and P.\,Bergman\inst{2}
   \and P.\,Bernath\inst{3}
   \and U.\,Frisk\inst{4}
   \and M.\,Olberg\inst{2}
   \and L.\,Pagani\inst{5}
\and L.M.\, Ziurys\inst{6}
}

\institute{Stockholm Observatory, AlbaNova University Center, SE-106
91 Stockholm, Sweden\\ \email{aage@astro.su.se}
   \and Onsala Space Observatory, SE-439 92 Onsala, Sweden
   \and Department of Chemistry, University of York, Heslington, York,
   YO10 5DD, UK
   \and Swedish Space Corporation, P. O. Box 4207, SE-171 04 Solna,
   Sweden
   \and LERMA \&\  UMR8112 du CNRS, Observatoire de Paris, 61,
   FR-75014 Paris, France
   \and Arizona Radio Observatory, Steward Observatory, University of
   Arizona, Tucson, AZ 85721, USA
}

\offprints{\\ Aage Sandqvist, \email{aage@astro.su.se}}


\date{Received 22 January 2008 / Accepted 28 February 2008}


\abstract {} {The Odin satellite has been used to search for the 
118.75-GHz
   line of molecular oxygen (O$_{2}$) in the Galactic centre.} {Odin
   observations were performed towards the Sgr\ts$\rm {A}^{*}$\ 
circumnuclear
   disk (CND), and the Sgr\ts A\ +20 \,{km\,s$^{-1}$}\ and +50
   \,{km\,s$^{-1}$}\ molecular clouds
   using the position-switching mode. Supplementary ground-based
   observations were carried out in the 2-mm band using the ARO Kitt
   Peak 12-m telescope to examine suspected SiC features.} {A strong
   emission line was found at 118.27 GHz, attributable to the $J=13-12$
   HC$_{3}$N\ line. Upper limits are presented for the 118.75-GHz O$_{2}$\
   $(1_{1}-1_{0})$ ground transition line and for the 118.11-GHz
   $^{3}\Pi_{2}, J=3-2$\ ground state SiC line at the Galactic
   centre. Upper limits are also presented for the 487-GHz O$_{2}$\ line in
   the Sgr\ts A\  +50 \,{km\,s$^{-1}$}\  cloud and for the 157-GHz,
   $J=4-3$, SiC line in the
   Sgr\ts A\   +20 and +50 \,{km\,s$^{-1}$}\ clouds, as well as the
   CND. The CH$_{3}$OH
   line complex at 157.2 - 157.3 GHz has been detected in the +20 and
   +50 \,{km\,s$^{-1}$}\  clouds but not towards Sgr\ts$\rm
   {A}^{*}$/CND.} {A $3\sigma$\
   upper limit for the fractional abundance ratio of [O$_{2}$]/[H$_2$] is
   found to be $X$(O$_{2}$) $\le 1.2 \times 10^{-7}$ towards the Sgr\ts A\
   molecular belt region.}


\end{document}



*************************************************************
Aage Sandqvist (Prof.)               Tel. +46-8-55378523
Stockholm Observatory		     Fax. +46-8-55378510
SCFAB-AlbaNova
SE-106 91 Stockholm                  email: aage@astro.su.se
Sweden
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