Title : Chemical Evolution Of Molecular Clouds

Masatoshi Ohishi; NAOJ, Mitaka, Japan

Molecular abundances of the interstellar clouds are believed to be
directly related with those of the Pre-Solar systems, because the
pre-solar systems are formed through gravitational contaction of the
interstellar clouds. We made extensive molecular spectral line surveys
toward a typical dark cloud, TMC-1, and a huge molecular cloud in the
Galactic Center, SgrB2, to derive precise molecular abundances of the
clouds, and to study chemical evolution of molecular clouds. The frequency
ranges observed were 8 - 50 GHz for TMC-1 and 30 - 270 GHz for SgrB2.

The results toward TMC-1 represent a typical molecular abundaces in an
early phase of the gravitational contraction, and those toward SgrB2
show abundances after stars formed inside. In TMC-1 we found that there
are a lot of unsaturared species, such as long carbon-chain molecules,
while saturated molecules were found very rich toward SgrB2(N), one of
our observed position in the SgrB2 cloud where a massive star has just
formed. Toward SgrB2(N) we detected CH3OH, C2H5OH, CH3COOH, NH2CHO, NH2CN,
etc., which are interesting pre%ebiological species. The formation of
 these
saturated molecules seem to be related with reactions on the dust grains.
We also checked the existence of the simplest amino acid, glycine, but
the signals from glycine have intensities lower than our detection limit.