Emission from CO Band Heads in Young Stellar Objects

Line emission from carbon monoxide at the positions of the delta-v = 2 band heads has been detected in three young stellar objects (S106 IR, NGC 2024/IRs 2, GL 2789) and in MWC 349 out of 16 objects in which it has been searched for. Previously band head emission had been reported among young stellar objects only in the Becklin-Neugebauer object and the Rho Ophiucus source, WL 16. The excitation mechanisms for the CO in the new objects appears to be the same as that deduced by Scoville et al. (1979, 1983) for BN, i.e., collisions within a dense, hot, and compact region near the star. In at least some of the objects this region is probably a circumstellar disk.