CO and [CI] in Nearby Galaxies: Probing Physical and Chemical Conditions

Observations of CO can provide constraints on the density and temperature of the dense star-forming gas in galaxies, while observations of [C I ] trace photon-dominated regions and provide information on the amount of atomic carbon in molecular clouds. In this paper, I review CO and [C I ] observations of nearby galaxies, with an emphasis on galaxies for which high-resolution observations of multiple transitions and isotopologues are available. …