Seeking Self-Regulating Simulations of Idealized Milky Way-Like Galaxies

Precipitation is potentially a mechanism through which the circumgalactic medium (CGM) can regulate a galaxy's star formation. Here we present idealized simulations of isolated Milky Way-like galaxies intended to examine the ability of galaxies to self-regulate their star formation, particularly via precipitation. Our simulations are the first CGM-focused idealized models to include stellar feedback due to the explicit formation of stars. We also examine the impact of rotation in the CGM. Using six simulations, we explore variations in the initial CGM $t_{\rm cool}/t_{\rm ff}$ ratio and rotation profile. Those variations affect the amount of star formation and gas accretion within the galactic disk. Our simulations are sensitive to their initial conditions, requiring us to gradually increase the efficiency of stellar feedback to avoid destroying the CGM before its gas can be accreted. Despite this gradual increase, the resulting outflows still evacuate large, hot cavities within the CGM and even beyond $r_{200}$. Some of the CGM gas avoids interacting with the cavities and is able to feed the disk along its midplane, but the cooling of feedback-heated gas far from the midplane is too slow to supply the disk with additional gas. Our simulations illustrate the importance of physical mechanisms in the outer CGM and IGM for star formation regulation in Milky Way-scale halos.
Comment: 28 pages, 13 figures. Submitted to the Astrophysical Journal