Dust Evolution in Simulated Multiphase Galactic Outflows

Abstract

We present the first large-scale, high-resolution simulations of dusty, star formation feedback-driven galactic outflows. Using the Cholla hydrodynamics code, we investigate dust sputtering in these environments for grains ranging in size from $1-0.001~{\mu\mathrm{m}}$. We compare results for two feedback models: one representative of low-redshift nuclear starburst galaxies and one similar to high-redshift main sequence galaxies. In general, our simulations show that multi-phase outflows are capable of safely transporting a vast majority of their dust to large distances ($\sim10~\textrm{kpc}$) from the disk. This work also shows that environmental shielding in cool gas clouds boosts dust survival rates significantly. The evolutionary path of dust depends strongly on grain size. Large grains ($a\geq0.1~{\mu\mathrm{m}}$) can be transported efficiently in all phases. Smaller grains, however, experience significant destruction in the hotter phases. $0.001~{\mu\mathrm{m}}$ grains in particular are quickly sputtered in all but the coolest gas, resulting in these grains strongly tracing the cool phase in outflows. These results may also indicate the importance of in-situ formation mechanisms, such as shattering, for the small dust grains and PAHs observed in emission throughout outflows in nearby galaxies. Surprisingly, we find that the hot phase dominates the transport of dust that survives to populate the circumgalactic medium.