Detection of vibration-rotation band lines of shocked CO in Orion

Abstract

Three lines of the fundamental vibration-rotation band of CO have been detected in emission toward H2 Peak 1 in OMC-1. Both the velocities of maximum line intensity and the linewidths appear to be similar to those of the H2 S(1) line, implying that the bulk of the line emission occurs in a shock within the molecular cloud. The relative line intensities, which are coupled to the populations of rotational levels in the ground vibrational state, yield average gas temperatures of about 1000 K. The luminosity of the CO fundamental band is nearly one-half of that from shocked H2, a considerably larger fraction than has been predicted previously. A search for Br-alpha line emission at Peak 1 produced an upper limit for that line flux which, including extinction, is less than one percent of the H2 S(1) flux. 22 references.