Non-equilibrium Photoionization and Hydrodynamic Simulations of Starburst-driven Outflows

TL;DR

This paper models starburst-driven galactic outflows using non-equilibrium ionization simulations to better explain observed complex thermal and emission line structures, advancing understanding of outflow physics.

Contribution

It introduces a comprehensive approach combining hydrodynamic simulations with non-equilibrium ionization and radiative transfer calculations to predict emission lines in starburst outflows.

Findings

Non-equilibrium ionization states significantly affect emission line profiles.

Hydrodynamic models with NEI provide better explanations for observed outflow features.

Application of non-equilibrium cooling to H II regions in starburst galaxies.

Abstract

Starburst-driven galactic outflows in star-forming galaxies have been observed to contain complex thermal structures and emission line features that are difficult to explain by adiabatic fluid models and plasmas in photoionization equilibrium (PIE) and collisional ionization equilibrium (CIE). We previously performed hydrodynamic simulations of starburst-driven outflows using the MAIHEM module for non-equilibrium atomic chemistry and radiative cooling functions in the hydrodynamics code FLASH, and calculated emission lines in combined CIE and PIE conditions. In the present study, we consider time-dependent non-equilibrium ionization (NEI) states produced by our MAIHEM simulations. Through extensive CLOUDY calculations made with the NEI states from our hydrodynamic simulations, we predict the UV and optical emission line profiles for starburst-driven outflows in time-evolving non-equilibrium photoionization conditions. Our hydrodynamic results demonstrate applications of non-equilibrium radiative cooling for H II regions in starburst galaxies hosting cool outflows.