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%astro-ph/0605031


\documentclass{aa}  
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\usepackage{txfonts}
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\begin{document}
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	\title{ORGANIC MOLECULES IN THE GALACTIC CENTER.\thanks{Table 7 is only
	available in electronic at the CDS via anonymous ftp to
	cdsarc.u-strasbg.fr (130.79.125.5) or via
	http://cdsweb.u-strasbg.fr/Abstract.html}}
   	\subtitle{HOT CORE CHEMISTRY WITHOUT HOT CORES.}


\author{M. A. Requena-Torres\inst{1}, J. Mart\'in-Pintado\inst{1}, 
	A. Rodr\'iguez-Franco,
          \inst{1}\inst{2}
	  	S. Mart\'in\inst{3}, N. J. Rodr\'iguez-Fern\'andez\inst{4}, 
		and \mbox{P. de Vicente}\inst{5}
		}
   \offprints{M. A. Requena-Torres, \email{requena@damir.iem.csic.es}}
   \institute{Departamento de Astrof\'isica Molecular e Infrarroja, Instituto de
   	Estructura de la Materia-CSIC
		C\ Serrano 121, E-28006 Madrid, Spain
		\email{requena@damir.iem.csic.es}
	\and
		Escuela Universitaria de \'Optica, Departamento de Matem\'atica
		Aplicada (Biomatem\'atica), Universidad Complutense de Madrid, 
		Avenida Arcos de Jal\'on s/n, E-28037 Madrid, Spain.
	\and
		Instituto de Radioastronom\'ia Milim\'etrica
		Av. Divina Pastora 7, Local 20, E-18012 Granada, Spain
		\email{martin@iram.es}
	\and
		Observatoire de Bordeaux, L3AB (UMR 5804), CNRS/Universit\'e
		Bordeaux 1, BP 89, 2 rue de l'Observatoire, 33270 Floirac,
		France \\
   		\email{nemesio.rodriguez@obs.u-bordeaux1.fr}
	\and
		Observatorio Astron\'omico Nacional,
		Centro Astron\'omico de Yebes
		Apartado 148, 19080 Guadalajara, Spain
		\email{p.devicente@oan.es}
	}

   \date{}
   
% \abstract{}{}{}{}{} 
% 5 {} token are mandatory
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  \abstract
  % context heading (optional)
  % {} leave it empty if necessary  
   {}
  % aims heading (mandatory)
   {We study the origin of large abundances of complex organic molecules 
   in the Galactic center (GC).} 
  % methods heading (mandatory)
  {We carried out a systematic study of the complex organic molecules 
CH$_3$OH, C$_2$H$_5$OH, (CH$_3$)$_2$O, HCOOCH$_3$, HCOOH, CH$_3$COOH, H$_2$CO,   
and CS toward 40 GC molecular clouds. Using the LTE approximation, we 
derived the physical properties of GC molecular clouds 
and the abundances of the complex molecules.}
  % results heading (mandatory)
  {The CH$_3$OH abundance between clouds varies by nearly two orders of 
magnitude from 2.4$\times$10$^{-8}$ to 1.1$\times$10$^{-6}$. 
The abundance of the other complex organic molecules relative to that of 
CH$_3$OH is basically 
independent of the CH$_3$OH abundance, with variations of only a factor 4--8. 
The abundances of complex organic molecules in the GC
are compared with those measured in hot cores and hot corinos, 
in which these complex molecules are also abundant. 
We find that both the abundance 
and the abundance ratios of the complex molecules
relative to CH$_3$OH in hot cores are similar to those found in the GC clouds.
However, hot corinos show different abundance ratios than observed in 
hot cores and in GC clouds. The rather 
constant abundance of all the complex molecules relative to CH$_3$OH 
suggests that all complex molecules are ejected from grain mantles by shocks. 
Frequent ($\sim$10$^5\,$years) shocks with velocities $>$6$\,$km~s$^{-1}$ are
required to explain the high abundances in gas phase of complex organic molecules in
the GC molecular clouds.
The rather uniform abundance ratios in the GC clouds and in Galactic hot cores
indicate a similar average composition of grain mantles in both kinds of regions.
The Sickle and the Thermal Radio Arches, affected by UV radiation, show different 
relative abundances in the complex organic molecules due to the differentially
photodissociation of these molecules.
}
  % conclusions heading (optional), leave it empty if necessary 
   {}


\keywords{Astrochemistry -- 
	ISM: clouds --
	ISM: molecules --
	Radio lines: ISM --
	Galactic: center} 

   \maketitle
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\end{document}


%************************************************
%Miguel Angel Requena Torres
%Dpto. Astrofisica Molecular e Infrarroja
% Instituto de Estructura de la Materia(CSIC)
%C\ Serrano 121
% 28006, Madrid (SPAIN)
% Tel: (0034) 91 561 68 00 - Temp extension 2416
% Fax: (0034) 91 564 55 57
% http://www.damir.iem.csic.es
%************************************************