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 $1-0.001~{μ\mathrm{m}}$. 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 ($a\geq0.1~{μ\mathrm{m}}$) can be transported efficiently in all phases. Smaller grains, however, experience significant destruction in the hotter phases. $0.001~{μ\mathrm{m}}$ 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.

Figures (17)

• Figure 1: Projections of the gas surface density ($\Sigma_\mathrm{gas}$, top) and $a=0.1~{\mu\mathrm{m}}$ dust surface density ($\Sigma_\mathrm{dust}$, bottom) through the $xz$-plane for the nuclear-burst simulation at 10, 20, and $30~\textrm{Myr}$. Each panel shows the full extent of the $xz$-plane, $10\times20~\textrm{kpc}^2$. An animated version of this figure is available in the online article.
• Figure 2: Same as Figure \ref{['fig:m82_proj_evolve']}, but for the high-z simulation. An animated version of this figure is available in the online article.
• Figure 3: Dust surface density projections for $1$, $0.1$, and $0.01~{\mu\textrm{m}}$ radius dust grains at $30~\textrm{Myr}$. The top and bottom row shows the nuclear-burst and high-z simulations, respectively. An animated version of this figure is available in the online article.
• Figure 4: Radial profiles for the hot (left), intermediate (middle), and cool (right) phases of the nuclear-burst (black) and high-z (pink) simulations, measured using $30^\circ$ cones opening away from the disk mid-plane. From top to bottom, the panels show gas number density, radial velocity, pressure, and temperature (all density-weighted). The dotted and dashed lines show the mean and median of each quantity, respectively, and the shaded regions show the 25th and 75th percentile range. The solid lines show power law fits to the median density profiles.
• Figure 5: Density (left) and temperature (right) slices through the center of the $xz$-plane of the nuclear-burst (top) and high-z (bottom) simulations at 30 Myr. The solid diagonal lines in the left panels show the $30^\circ$ cones used to measure the gas and dust radial profiles described in Section \ref{['subsec:radial_profiles']}.