Abstract:
Molecular
clouds are the densest regions of gas in galaxies, in which localised
gravitational collapse leads to the formation of stars. I will present
an overview of the theory of how molecular clouds form in galaxies, and
show how simulations demonstrate the regimes over which different
theoretical models apply. I will also discuss the physics of spiral arms
and how star formation and molecular clouds relate to the spiral arms
in galaxies. Recent simulations show that molecular clouds appear to be
largely independent of the nature of spiral arms (which fortunately
means that smaller scale simulations of star formation can effectively
ignore the larger scale processes such as galaxy interactions which
drive spiral arms), although the properties of the molecular clouds and
resulting star formation are dependent on the strength of the spiral
arms. Time permitting, I will relate the local properties of the gas in
galaxies, such as density and velocity field, to the resulting stellar
clusters which form, again both theoretically and through numerical
simulations.