The GHOSDT Simulations (Galaxy Hydrodynamical Simulations with Supernova-Driven Turbulence) -- I. Magnetic Support in Gas Rich Disks

TL;DR

This paper introduces GHOSDT, a suite of magneto-hydrodynamical simulations that reveal magnetic fields significantly influence the structure and star formation activity in gas-rich galactic disks at high redshift.

Contribution

The study presents high-resolution MHD simulations showing magnetic pressure's role in dense ISM, establishing a relation between magnetic field and gas surface density, and aligning results with theoretical models.

Findings

Magnetic fields increase cold gas fraction by up to 40%.

Magnetic pressure reduces disk scale height by about half.

Magnetic field strengths in dense gas match observed values.

Abstract

Galaxies at redshift $z\sim 1-2$ display high star formation rates (SFRs) with elevated cold gas fractions and column densities. Simulating a self-regulated 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, 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 disc scale height by up to a factor of $\sim 2$, and reduces the star formation burstiness. In dense ($n>100\;\rm{cm}^{-3}$) gas, we find steady-state magnetic field strengths of 10--40 $\mu$G, comparable to those observed in Galactic molecular clouds. Finally, we demonstrate that our simulation framework is consistent with the Ostriker et al. (2022) Pressure Regulated Feedback Modulated Theory of star formation and stellar feedback.