The link between star formation and gas in nearby galaxies

How galaxies form their stars has been extensively studied but the role of the galactic gas content and the efficiency of its conversion into stars remain to be fully understood. Here the author presents a data-driven statistical analysis that reduces potential biases related to non-detections to quantify the link between star formation, molecular, and neutral gas in nearby galaxies. Observations of the interstellar medium are key to deciphering the physical processes regulating star formation in galaxies. However, observational uncertainties and detection limits can bias the interpretation unless carefully modeled. Here I re-analyze star formation rates and gas masses of a representative sample of nearby galaxies with the help of multi-dimensional Bayesian modeling. Typical star forming galaxies are found to lie in a 'star forming plane' largely independent of their stellar mass. Their star formation activity is tightly correlated with the molecular and total gas content, while variations of the molecular-gas-to-star conversion efficiency are shown to be significantly smaller than previously reported. These data-driven findings suggest that physical processes that modify the overall galactic gas content, such as gas accretion and outflows, regulate the star formation activity in typical nearby galaxies, while a change in efficiency triggered by, e.g., galaxy mergers or gas instabilities, may boost the activity of starbursts.