, S. Liechti
, C.M. Walmsley
, and F. Colomer
Centro Astronómico de Yebes, Apartado 148, E-19080 Guadalajara, Spain
Physikalisches Institut, Universität zu Köln, Zulpicherstr. 77,
D-50937 Köln, Germany 
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, 3
--2
, and
5
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thermal lines of CH
OH toward young bipolar
outflows. Strong emission ( > 
6 K, in the case of L 1157) is
observed toward the shocked molecular regions associated with the
lobes of some outflows, whereas the emission from the cold quiescent
material in the surrounding molecular core is rather weak ( < 
1
K). We have derived the methanol abundance by combining the CH
OH
data with new C
O observations. It results that methanol is
enhanced by large factors toward the shocked regions (
400
toward the blue-shifted lobe of L 1157). Although the shocked gas
is known to be heated to about 100 K, the CH
OH rotation
temperatures have moderate values: in L 1157 
increases from 8 K in the ambient gas to 12 K in the shocked
region. Radiative transfer calculations, carried out to simulate the
CH
OH excitation in different physical circumstances, confirm
that in the range of physical conditions discussed here the methanol
molecules are very subthermally excited, and 
is not a
good measure of the kinetic temperature (
<< 
). The observed methanol abundance enhancements are likely caused
by processes of desorption of grain mantles in shocks.