Speaker
Chang-Goo Kim
(Princeton University)
Description
Supernova (SN) explosions inject a prodigious amount of energy into the interstellar
medium (ISM). This powerful feedback implies that SNe are a major driver of
turbulence and galactic winds, and may be the dominant regulator of star formation
(SF) in disk galaxies. Our understanding of the interaction of SN(e) with the ISM
have gradually improved over many decades. However, a complete and self-consistent
gas-dynamical model of the ISM including SN(e) is still numerically challenging, and
for many years the effect of SN feedback has been both underestimated (based on
poorly resolved numerical simulations) and overestimated (based on classical analytic
theories with unconfirmed assumptions). In this talk, I first revisit the evolution
of radiative SN remnants in the two phase ISM driven by single and multiple SN(e) and
provide the condition for SNR evolution to be numerically resolved. This shows that
(1) the inability of SNe to limit SF in many galaxy formation simulations has been
due to lack of resolution, and (2) classical analytic models do not properly account
for cooling during post-Sedov SNR evolution. I then present a theoretical and
numerical framework for self-regulation of the star formation rates (SFRs) in disk
galaxies. The theory assumes (1) force balance between pressure support and the
weight of the ISM, (2) thermal balance between radiative cooling in the ISM and
heating via FUV radiation from massive young stars, and (3) turbulent energy balance
between dissipation in the ISM and driving by momentum injection of SNe. Numerical
simulations show vigorous dynamics in the ISM at all times, but with proper temporal
and spatial averages, all the expected balances hold. This leads to a scaling
relation between mean SFRs and galactic gas and stellar properties, arising from the
fundamental relationship between SFR surface density and the total midplane pressure.
Finally, I shall show results from a new ISM/SF simulation of the solar neighborhood
that follows space-time correlation of SNe with dense and diffuse gas realistically,
resolves all thermal phases of the ISM, and fully captures the circulation of the
galactic “fountain.” A fast, ``hot’’ galactic wind is launched with a mass loading
factor of 0.1-1, while the SFR is self-regulated consistent with expectations within
the warm and cold ISM.
Primary author
Chang-Goo Kim
(Princeton University)
