Galaxies 09: Assembly, Gas Content and Star Formation History of Galaxies
Philip Hopkins
UC Berkeley
The Role of Gas in the Formation of Disks and Bulges: More Important than You Think
In the last few years, the combination of models that include realistic large gas supplies in galaxies, and prescriptions for feedback from both stellar evolution and super-massive BHs to maintain those gas reservoirs, have led to huge shifts in our understanding of galaxy formation and may represent the solution to many outstanding problems in galaxy formation. In particular, gas-richness may represent the most important driving factor in the effects of galaxy-galaxy mergers. The degree of gas-richness in mergers has dramatic effects on bulge structural properties, stellar populations, mass profiles, and kinematics; models with the appropriate gas content have finally begun to produce realistic bulges that resolve a number of discrepancies and make unique predictions that allow for new observational probes of bulge merger histories. In the regime of very gas-rich mergers, expected at high redshift and/or low masses, gas can qualitatively change the character of mergers, making disks robust to destruction in mergers and providing a natural explanation for the observed morphology-mass relation. Ignoring the effects of gas in changing the dynamics of galaxy assembly has order-of-magnitude consequences for observed galaxy demographics.
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