Dr. Eve Ostriker (Associate Chair of the Department of Astrophysical Sciences and the Lyman Spitzer, Jr., Professor of Theoretical Astrophysics at Princeton University)

Thursday, October 13, 2022
3:45 p.m.
LGRT 1033


The Two Faces of Star Formation Feedback


In recent years, a major focus of research in galaxy formation and evolution has been on the ability of feedback to limit star formation. This happens at the scale of individual giant molecular clouds (GMCs), which are destroyed largely as the result of the radiation input from massive stars, and at the scale of whole galaxies, in which star formation can be quenched by the ejection of baryons in multiphase galactic superwinds. To understand this “face” of feedback in quantitative detail, high-resolution numerical radiation magnetohydrodynamic (RMHD) simulations with very high spatial resolution and accurate algorithmic implementations for key physical processes are required. I will report on recent results from our group based on simulations of this kind, which (1) allow us to distinguish the relative importance of photo-evaporation and radiation pressure on cloud destruction as a function of GMC properties, and produce observed GMC lifetimes and star formation efficiencies consistent with observations; and (2) provide predictions for the mass, energy, and metal loading scaling relations of galactic winds as a function of the large scale star formation rate. The second “face” of star formation feedback is its role — via radiation and supernovae -- in providing the heating and input of kinetic energy that offsets cooling and dissipation, in order to maintain the observed thermal, turbulent, and magnetic pressure in the three-phase ISM. Our numerical RMHD simulations and associated theory have also advanced understanding of this aspect of feedback, demonstrating that star formation and the ISM reach a co-regulated equilibrium state for a wide range of conditions in disk galaxies. I will argue that it is this equilibrium that underlies observed star formation scaling relations in disk galaxies, and that simple feedback “yield” parameters that encapsulate the complexities of heating/cooling and driving/dissipation processes can be used to predict star formation rates based on the large-scale gas and stellar contents of galaxies, in good agreement with observations. All graduate students and postdocs are welcome and encouraged to join the speaker for an informal lunch discussion from 12:30-1:30 in LGRT 533, which can be attended remotely via https://umass-amherst.zoom.us/j/97165107867. Please let John Weaver know if you are interested in attending dinner with the speaker on Thursday evening, the location of which is TBD.

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