Contents of: VI/111/./abstract/JCERNICH_MAS_AGUA.abs

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==> In this proposal, more time is requested for JCERNICH.CERNI_1
For  many  years  the  extent of water emission and its abundance in molecular
clouds  have  been key problems in the study of the interstellar medium (ISM).
Although  all  chemical  models  predict  a high water abundance, ground-based
observations  of  non-masering rotational transitions of water are practically
impossible. Recently, Cernicharo et al. (1990, 1994) succeeded in observing at
183  GHz  the  weakly  masering  313-220 transition of water in many molecular
clouds  opening  a new window to study water in the ISM. In particular, it was
shown  for  the  first time that water emission in Orion is spatially extended
(see  Fig 1). The derived abundances demonstrate that water is one of the most
abundant  molecular species in warm molecular clouds. In proposal CERNI_1, for
which  we  obtained  high  priority  time, we have observed SgrB2 and obtained
spectacular  results concerning the water extent and its excitation conditions
(see  Fig  2).  We  would  like to increase the size of the raster obtained in
SgrB2  and  that  of  those that are being done now in other sources (from the
same  proposal  CERNI_1).  The  main  new source in this follow up is Ori-IRC2
which was our main source in the case of a spring launch of the ISO satellite.
We  would  like to combine LWS01, LWS04 and SWS06 (vibrational bending band of
water) observations on the proposed sources.
ISO  is  the only instrument in the next decade which will allow to observe at
high spatial resolution and sensitivity the thermal emission of water vapor in
the  ISM.  The angular resolution of ISO in the far-infrared together with the
sensitivity  of  the  LWS  FP  spectrometer will enable to map and resolve the
large  scale  distribution  of  water  in  molecular clouds. We propose to map
several  nearby  molecular  clouds  in  two  lines of H2O connecting low-lying
energy  levels.  Other  transitions  of  water  and  its  rare  HH18O  isotope
(absolutely  necessary in view of the large opacities involved in H2O) will be
made  towards  selected  positions  in  these  molecular  clouds. The proposed
observations  will  provide  a major contribution from ISO to our knowledge of
the role of water in the chemistry and physics of the interstellar medium.

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