The KOSMA Multi-line CO Survey of Clouds in the Galactic Molecular Ring

Abstract

The Milky Way is known to be a spiral barred galaxy with a prominent ring between 4 and 7 kpc Galactocentric radius (Scoville & Solomon 1975; Clemens et al. 1988). Ring resonances occur frequently in barred spiral disk galaxies by gas accumulation under the continuous influence of gravitational torques from the bar pattern. As density enhancements they are often sites of increased star formation (Buta 1999). In an alternative view, this part of our Galaxy can be separated into two spiral arms, the Sagittarius and the Scutum(Cohen et al.1980). The Galactic Molecular Ring (GMR) shows up prominently in CO J=1-0 (Dame et al. 2001) as well as in Ci, Cii, and Nii in the COBE survey (Fixsen et al.1999). Due to its high star formation rate, most of the Galactic giant Hii regions, maser sources, and SN remnants are observed towards the ring and most of the Galaxy’s FIR luminosity is emitted here (Burton et al. 1976, Bloemen et al. 1990).