MOLECULAR CLOUDS ASSOCIATED WITH LUMINOUS FAR-INFRARED SOURCES IN THE OUTER GALAXY

The stellar content and physical properties of the molecular clouds associated with 21 bright far-infrared sources in the outer Galaxy have been determined through 12CO, 13CO, 6 cm radio continuum, and IRAS observations. The molecular cloud masses range from 200 to ∼104 M⊙. The far-infrared luminosity-to-mass ratio for these clouds has a mean value of 6.8 L⊙/M⊙ and shows no correlation with the cloud mass, a result similar to that found for more massive clouds in the inner Galaxy. The radio continuum survey of the 21 bright far-infrared sources indicates that most of these regions probably have a single, massive star providing most of the ionization. The cloud masses derived from virial and LTE analyses are in agreement, supporting the assumptions commonly made in their calculations, and we find a tight, near-linear correlation between the 12CO luminosity and the cloud mass. The H2 column density and integrated 12CO intensity are also correlated on a point-by-point basis, although the scatter is larger than the 12CO luminosity-cloud mass relation.