Warm and cold molecular gas in galaxies

New and archival interferometric (CO)-C-12 ( 1 --> 0) data sets from six nearby galaxies are combined with H-2 2.122 mu m and H alpha maps to explore in detail the interstellar medium in different star-forming galaxies. We investigate the relation between warm (H-2 at T similar to 2000 K) and cold (CO at T similar to 50 K) molecular gas from 100 pc to 2 kpc scales. On these scales, the ratio of warm-to-cold molecular hydrogen correlates with the f(nu)(60 mu m)/f(nu)(100 mu m) ratio, which tracks the star formation activity level. This result also holds for the global properties of galaxies from a much larger sample drawn from the literature. The trend persists for over 3 orders of magnitude in the mass ratio, regardless of source nuclear activity.