Observations of Interstellar CO at MM and UV Wavelengths and Diverse Comments on Interstellar Diffuse Lines

Abstract

The directions of stars known to exhibit the molecule CN in their interstellar spectra were searched for CO at both millimeter and ultraviolet wavelengths in order to obtain more information about moderately dense interstellar material, which is of value in ascertaining the dynamics of star formation. Results show that where both CO and CN have been observed in the same line of sight most of the CO and CN coexists, and limited data for CH indicates that it also coexists with the other two types of molecules. The detections of CO are in broad agreement with model chemical reaction schemes and support the predicted trend in the value of the ratio N(CN)/N(CO) by showing that this ratio is larger at moderate densities than the ratio found for higher density clouds. In addition, preliminary observations of diffuse interstellar features at 5778, 5780 and 5797 A show a wider than expected range of behavior for these lines and may give some further indications about the identity of the carriers of the diffuse absorption.