Recent Work on the Interstellar Medium

Emphasis in this review of current problems in the study of the interstellar medium is on a few specialized topics. The first treated is the problem of the cloud structures and the velocity fields in the interstellar gas. Another section deals with the observations suggesting the presence of dust as well as gas in the medium and with the proposed nature of the dust grains. These grains were the first indicators of the presence of a general galactic magnetic field and are believed to be catalytic agents in the formation of molecules in the gas. The status of current observational investigations of the magnetic field and of current theoretical studies of the formation of interstellar molecules is described. Finally, very recent observations in the microwave spectrum of the hydroxyl radical are outlined. These suggest the availability of new and surprising information about conditions in the interstellar medium.