The Large-Scale Regulation of Star Formation in Disk Galaxies
Eve Ostriker (U. Maryland) - Oct 15, 2009 at 12:10 pm
Star formation in disk galaxies takes place in cold, dense clouds
containing millions of solar masses of molecular gas. These clouds
are very dynamic, forming out of diffuse interstellar gas, undergoing
local collapse to produce clusters of stars, and then dispersing due
to energetic feedback from star formation. Recent numerical
simulations have shown how self-gravitating ISM compression results in
strings of HII regions that light up spiral arms, and creates interarm
structures seen in high-resolution HST and Spitzer images of grand
design spirals. Simulations including a multiphase ISM have been
able
to reproduce observed relationships between large-scale gas properties
and star formation rates in nearby disk galaxies, and have
demonstrated how feedback-driven turbulence and environment (including
the rotation rate and the stellar disk's gravity) are crucial in
setting these rates on ~kpc scales. These results help to explain
why
observed molecular-to-atomic mass ratios and star formation rates
correlate with the mean midplane pressure. In addition, they
suggest
that empirical Kennicutt-Schmidt relations between star formation rate
and gas surface density arise in part as a result of long-term
galactic evolution toward Toomre parameters near unity. In
discussing
these recent results, I will also highlight the importance of
resolving disks' vertical structure in numerical models, in order to
obtain reliable measures of the star formation rate.
The seminar will be held in 544 Campbell Hall.
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