Starburst heating and synthetic ion column densities in multiphase galactic outflows

TL;DR

This study uses magnetohydrodynamical simulations to explore how magnetic fields and UV radiation influence ion production, especially N V, in multiphase galactic outflows, revealing effects on spectral line characteristics.

Contribution

It demonstrates the combined impact of magnetic fields and UV background proximity on ion column densities and spectral line profiles in galactic wind simulations.

Findings

Magnetic fields broaden N V absorption lines by shielding dense gas.

Distant UV background results in N V only in outer cloud layers with no spectral signature.

Nearby UV radiation produces narrow N V lines in cloud cores.

Abstract

Stellar-driven galactic winds are multiphase outflows of energy and matter connecting the interstellar and circumgalactic media (CGM) with the intergalactic medium. Galactic winds contain a hot and diffuse phase detected in X-rays, and a cold and dense phase detected via emission and absorption lines from the ions populating the outflow. The ion production within galactic winds largely depends on the background UV radiation field produced by star formation, and this in turn depends on the age of the starburst, the gas metallicity, the proximity of the outflowing gas to the central star-forming regions. Our study probes the influence of the proximity of wind-cloud systems to the UV background source, and the effects of magnetic fields on the N V ion production through the analysis of synthetic column densities and spectral lines. We utilise magnetohydrodynamical simulations to study weakly-magnetised wind-cloud systems, and extract synthetic spectral lines with Trident and yt. Our simulations indicate that magnetic fields transverse to the wind have a shielding effect on dense gas, producing broader N V absorption lines. Also, a weak (distant) UV background produces N V only in the outer cloud layers with no spectral signature, while a strong (nearby) UV background produces it in the cloud core with a narrow spectral line. Overall, transverse magnetic fields and a UV radiation at 50 kpc produce the stronger N V spectral lines.