Star Formation and Feedback: A Modern Primer

The cosmic history of galaxy formation is the history of star formation writ large.  Some of the most important processes affecting galaxy evolution involve coupling between stellar and gaseous components, since massive stars are the primary energy source in the interstellar medium (ISM).  The majority of stellar energy — including UV radiation, winds, and supernovae — is returned rapidly after a given population of stars forms, and is therefore collectively termed “star formation feedback.” I will review current theory of the physics of feedback, showcasing results from state-of-the-art, high-resolution numerical radiation-magnetohydrodynamic simulations that directly follow multiphase ISM evolution including the effects of UV radiation, stellar winds, and supernovae. These simulations, on both scales of individual star-forming molecular clouds, and scales of galactic disks, show star formation efficiencies and rates that are consistent with detailed observations in the nearby universe, and also indicate strong sensitivity to environment. At high densities and where dust and metal abundances are high, stellar radiation does not propagate as far, and cooling rates are enhanced. As a result of the reduced effectiveness of feedback in maintaining the ISM pressure (turbulent, thermal, and magnetic), star formation rates and efficiencies are expected to increase in high-density, high-metallicity environments. Results from suites of resolved star-forming ISM simulations have been used to calibrate new subgrid models, and incorporation of these new results in galaxy formation models may potentially significantly change predictions for star formation at high redshift.