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Astron. Astrophys. 323, 357-362 (1997)
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Search for 183 GHz water maser emission in starburst galaxies
F. Combes ,
Nguyen-Q-Rieu and
Dinh-V-Trung
DEMIRM, Observatoire de Paris, 61 Av. de l'Observatoire,
F-75014 Paris, France
Received 18 November 1996 / Accepted 13 January 1997
Abstract
We have searched for water vapor emission at 183 GHz, redshifted at
157 GHz and 161 GHz, in the two ultraluminous starburst galaxies Mkn
1014 and VIIZw244. Due to the low energy level of the upper state of
the 183 GHz transition (![[FORMULA]](img1.gif)
200K), it is expected
that the emission regions are extended, as they are in the Orion or
W49N molecular cloud cores. Since the warm and dense gas, typical of
star-forming cores, is expected to have a large surface filling factor
in ultraluminous starburst galaxies, the maser H2 O
emission at 183 GHz could have been detected. In fact, no water line
has been detected in Mkn 1014 and VIIZw244 with an upper limit of
![[FORMULA]](img2.gif)
= 1 mK. We compare the H2 O/CO
emission ratio with that obtained towards the ultraluminous high-z
object F10214+4724, and suggest that the amplification factor for the
H2 O emitting cores in this galaxy should be higher than
for the general CO emitting region. We conclude that the warm and
dense H2 O cores are much less extended in the two observed
starburst galaxies than in the Orion molecular cloud; this provides
some information on the physical conditions and cooling processes of
the interstellar medium in starburst galaxies.
Key words: masers 
galaxies: ISM
galaxies:
starburst
radio lines:
galaxies
galaxies: Mkn 1014; VIIZw 244
Send offprint requests to: F. Combes (bottaro@obspm.fr)
© European Southern Observatory (ESO) 1997
Online publication: June 5, 1998
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