Gas dynamics and structure of galaxies

Between gas dynamics and structure of galaxies is a two-way relation. On one hand, gas dynamics in a galaxy is largely determined by the structure of the galaxy, and on the other hand, gas dynamics can gradually alter the galaxy structure through redistribution of mass and angular momentum within the galaxy. The first half of this relation should mostly determine gas distribution and regulate star formation in undisturbed spirals, and the second half has been suggested to cause secular evolution of spiral galaxies—a slow mode of galaxy evolution in the absence of major mergers. Our knowledge on this relation is going to be greatly deepened by the ALMA. Focusing on the galaxy evolution through gas dynamics, I briefly review what we know about the subject. Then I try to look out what the ALMA can do to answer open questions in the field. It is pointed out that the ALMA will be able to fully map all the spiral galaxies between 1 and 25 Mpc at 1″ resolution in 1000 hours.