Galactic structure from observations of interstellar calcium lines. I. Analysis of the radial velocities.
Summary. As part of a galactic survey the distribution and kinematics of the interstellar calcium are investigated from 1=2850, through the galactic center to 1=290. 122 radial velocities of interstellar calcium lines have been measured in 68 0-B stars with a dispersion of 12.3 A mm ' in La Silla Observatory (ESO). The kinematical distances are calculated from Schmidt's modeL The data from interstellar calcium and 0-B stars shows two spiral arms and a possible third one. In the Carina region the residual velocities are not significanL In the longitude range 1= the radial velocities of interstellar calcium show 2 maxima, and two arms are observed as clearly separated as the well known Perseus arm and the local arim In addition, 8 radial velocities are found ranging from -70 to -97kms '. Near l=00,acomponent at -26kms ' is seen in a distant star. This may be an expansion feature at a distance of about 4.5 kpc. In the longitude range 1= we have found the Sagittarus spiral arm. The extension of the Norma-Centaurus arm in this region has been attempted. The Carina-Sagittarus arm is seen from 1=2850 to 1=290 Key words: galactic structure - interstellar calcium lines - radial velocities
Astronomy and Astrophysics
- Pub Date:
- January 1973