Institute for Advanced Study Informal Astrophysics Seminar

We use local three-dimensional magnetohydrodynamic simulations to investigate the quasi-equilibrium states of galactic disks regulated by star formation feedback. We incorporate effects from massive-star feedback via time-varying heating rates and supernova (SN) explosions. We find that the ISM disks in our simulations rapidly approach a quasi-steady state that satisfies vertical dynamical equilibrium. The SFR surface density self-adjusts to provide the total momentum flux (pressure) in the vertical direction that matches the weight of the gas. The final (time-averaged) state is insensitive to initial conditions and vertical boundary conditions. We quantify feedback efficiency by measuring ``feedback yields’’ defined by the ratio between different pressure components and the SFR surface density. For both magnetized and unmagnetized models, the turbulent and thermal yields are the same. In magnetized models, turbulent magnetic fields are rapidly generated by the small-scale turbulence dynamo, and saturate at a level corresponding to the equipartition with the turbulent kinetic energy. The presence of magnetic fields enhances the total feedback yield and therefore reduces the SFR, since the same vertical support can be supplied at a smaller SFR. Since additional vertical support can be provided by mean magnetic fields in the azimuthal direction, the SFRs are even more reduced in strongly magnetized models.