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1Nobeyama Radio Observatory, National Astronomical Observatory, Minamimaki, Minamisaku, Nagano 384-1305, Japan 2Okayama Astrophysical Observatory, National Astronomical Observatory, Kamogata, Asakuchi, Okayama 719-0232, Japan 3Department of Astronomy, Faculty of Science, the University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan 4Kiso Observatory, Institute of Astronomy, Faculty of Science, the University of Tokyo Mitaka, Tokyo 181-8588, Japan 5Mizusawa Astrogeodynamic Observatory, National Astronomical Observatory, Mizusawa, Iwate 023-0861, Japan 6Astronomical Institute, Osaka Kyoiku University, Asahigaoka, Kashiwara, Osaka 582-8582

概要:

A survey has been made in the SiO J=1-0, v=1 and 2 transitions ( GHz) for the color-selected IRAS sources in the galactic disk area of -10 <l<35 and |b| < 3 with the Nobeyama 45-m telescope. At present, we have detected about 300 out of 500 observed sources in SiO masers. Distances to the sources are deduced by the JHK, IRAS 12, and 25 flux densities and range approximately from 2 kpc to 12 kpc. The lines of sight of this region cross the location of the near end of the bar in the Galaxy. Radial velocities of the detected sources spread between -200 and 300 . The range slightly exceeds the possible limits expected from the galactic rotation. The SiO velocity-longitude (v-l) diagram exhibits several concentrations of sources in narrow ranges in longitude and velocity and also exhibits empty regions. A comparison with the CO and HI v-l diagrams reveals that the overall distribution of the SiO maser sources on the v-l diagram resembles to the molecular ring feature. A group of stars at l shows an odd velocity of 85 , at which no corresponding CO cloud is found. The stars with a large deviation of motion from the galactic rotation are found to fall at a distance of 5.5 kpc from the Sun. This fact might indicate that the stellar motion deviates strongly from smooth galactic rotation near to the tip of the bar.





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Next: 1 Introduction



Jun Makino
Wed Mar 17 17:53:42 JST 1999