Interstellar lines in stars at high galactic latitudes

Abstract

We have measured the velocity and equivalent widths of the optical interstellar lines in a group of southern B stars at high galactic latitudes, as well as additional data for the stars previously discussed by Münch and Zirin. The main peculiarities of the interstellar matter far above the plane seem to be an increase in the ratio of the column density of Ca ii to that of Na i and, less certainly, an excess of Ca ii relative to H i. The gas-to-dust ratio indicates that some of the hydrogen at high galactic latitudes may be ionized.