On the velocity structure of the interstellar clouds near rho Ophiuchi

Accurate radial velocities of the optical interstellar features for some of the B stars embedded in the ρ Oph complex are obtained by averaging results of several photographic high-dispersion spectra. In at least one case, there is a real difference between the radial velocity of the atomic features (Na i and Ca ii) and the molecular ones (CH and CN). We show that it is probable that the CH and CN are concentrated either in a separate cloud (i.e., region of space) from the Ca ii and Na i or in a cloud whose outer parts are expanding rather than in a single cloud which is contracting or rotating.