Diffuse molecular clouds
type: Concept
contributor: AAS Frey.Katie
broader: Molecular clouds
definition: A type of molecular cloud in which the interstellar radiation field is sufficiently attenuated, so that the local fraction of molecular hydrogen becomes substantial (> 0.1). However, enough interstellar radiation is still present to photoionize any atomic carbon, or to photodissociate carbon monoxide (CO) such that carbon is predominantly still in the form of C+ (> 0.5). In steady state, diffuse molecular clouds must necessarily be surrounded by diffuse atomic gas, in order to provide the shielding of radiation. This means that most sightlines that cross a diffuse molecular cloud will also cross diffuse atomic gas.
modified: 2020-10-27T13:40:42.993Z
modified: 2020-10-27T13:40:31.904Z

Molecular clouds
type: Concept
narrower: Diffuse molecular clouds