The Galactic Distribution and Kinematics of OH stars (A Preliminary Discussion)

Preliminary results are presented of a large-scale 1612 MHz sky survey undertaken with the 300-ft radio telescope at the National Radio Astronomy Observatory to study the distribution and kinematics of OH stars. The longitude-velocity distribution of the stars is compared to the neutral hydrogen distribution (Kerr, 1969). The longitude-velocity distribution of the OH stars indicates that differential rotation is frequently a significant component of their motion. However, some sources have substantial noncircular velocities. The clustering of some OH stars near bumps in the high-velocity edges of the HI distribution and their proximity to regions of high HI brightness temperature suggest that they may be spatially related to concentrations of neutral hydrogen and are extreme Population I objects. There is a general increase in the number of stars towards the galactic center. It is suggested that there may be two types of sources, a younger population closely associated with the HI distribution and a possibly older population in which some members have large noncircular velocities.