OBSERVATIONS OF THERMAL TRANSITIONS OF SiO TOWARD THE SGR A MOLECULAR CLOUD

Sgr A 분자운의 열적 SiO 천이선 관측연구

  • MINH Y. C. (Korea Astronomy Observatory) ;
  • ROH D.-G. (Korea Astronomy Observatory) ;
  • KIM S. J. (KyungHee University, Dept. of Space Science) ;
  • OHISHI M. (National Astronomical Observatory of Japan)
  • Published : 2001.12.01

Abstract

We observed the thermal transitions of SiO (J=I-0, 2-1) and $^{29}SiO$ (J=l-O) toward the Sgr A molecular clouds. The distribution and the velocity structure of SiO are very similar to previous results for 'quiet' interstellar molecules. We think· that the SiO has been well mixed with other molecules such as $H_2$ which may indicate that the formation of Sgr A molecular clouds was affected by the activities, such as shock waves or energetic photons, from the Galactic center in large scales. The total column density of SiO is about $4.1\times10^{14} cm^{-2}$ and the fractional abundance $SiO/H_2$ appears to be about 10 times larger than those of other clouds in the central region of our galaxy. The derived values are thought to be lower limits since the optical depths of the observed SiO lines are not very thin. The formation of SiO has been known to be critically related to shocks, and our results provide informative data on the environment of our Galactic center.

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