Stellar Feedback Effects on the Mass Distribution of Clouds and Cloud Complexes

Galaxy evolution is sensitive to how stars inject feedback into their surroundings. In particular, stellar feedback from star clusters strongly affects gas motions and the baryonic cycle, with more massive clusters having stronger effects. Our previous results show that the star cluster mass distribution in dwarf galaxies depends on feedback, as strong pre-SN feedback, particularly ionizing radiation, results in fewer high-mass clusters. We investigate the mass distribution of gas clouds in dwarf galaxies. Since clusters form from collapsing gas clouds, we expect a similar feedback dependence in both distributions, so we hypothesize that pre-SN feedback yields fewer high-mass clouds. To test this, we use an isocontour analysis at cutoff densities of $10,\ 10^{1.5},\ 10^{2}$ cm$^{-3}$ to identify clouds in dwarf galaxy simulations run with the RAMSES adaptive mesh refinement code. We calculate mass distributions for models with different combinations of SNe, stellar winds, and ionizing radiation. We find that the mass distribution for clouds with $n>100$ cm$^{-3}$ is independent of feedback, but the distribution for complexes with $n>10$ cm$^{-3}$ is more top-heavy in the presence of radiation. Winds do not affect the distribution at any scale. This contradicts our hypothesis that cloud and cluster mass distributions respond similarly to feedback. Instead, the dense cloud mass function shows no feedback dependence, suggesting its shape is set by gravity. We conclude that the cluster mass function must be shaped by intra-cloud feedback regulating star formation and, in the case of radiation, effects on parent cloud temperature. (shortened)