The GHOSDT Simulations: I. Magnetic Support in Gas-rich Disks

Galaxies at redshift z ∼ 1-2 display high star formation rates with elevated cold gas fractions and column densities. Simulating a self-regulated interstellar medium (ISM) in a hydrodynamical, self-consistent context has proven challenging due to strong outflows triggered by supernova (SN) feedback. At sufficiently high gas column densities, if magnetic fields or other mitigating measures are not implemented, these outflows can prevent a quasi-steady disk from forming for several 100 Myr. To this end, we present GHOSDT (galaxy hydrodynamical simulations with SN-driven turbulence), a suite of magneto-hydrodynamical simulations that implement ISM physics at high resolution. We demonstrate that magnetic pressure is important in the dense ISM of gas-rich star-forming disks. We show that a relation between the magnetic field and gas surface density emerges naturally from our simulations. We argue that the magnetic field in the dense, star-forming gas may be set by the SN-driven turbulent gas motions. When compared to pure-hydrodynamical runs, we find that the inclusion of magnetic fields increases the cold gas fraction by up to 40%, reduces the disk scale height by up to a factor of ∼2, and reduces the star formation burstiness. In dense (n > 100 cm⁻³) gas, we find steady-state magnetic field strengths of 10-40 μG, comparable to those observed in Galactic molecular clouds. Finally, we demonstrate that our simulation framework is consistent with the E. C. Ostriker and C.-G. Kim pressure-regulated feedback-modulated theory of star formation and stellar feedback.