Star Formation and Gas Contents in Disk Galaxies: Complex Relationships

Star formation activity is highly variable in galaxies. Can we relate it to the gas content of the galaxy? To the gas composition, the relative amounts of available molecular and atomic hydrogen? Or are these variations mainly due to the galaxy environment? To study this problem, we made a statistical study of the links between the star formation indicators and gas tracers in a sample of 469 disk galaxies. Since the molecular phase is the place of star formation, information about the H2 content is crucial. Hence, the sample galaxies have all been observed in the 12CO(1-0) line. We use a conversion factor X = 2.3 1020. We studied the global properties of the sample objects: total gas content and global star formation indicators at various wavelengths from the optical colors to the radio continuum emission.