Photoionization analysis of chemo-dynamical dwarf galaxies simulations

TL;DR

This study combines chemo-dynamical dwarf galaxy simulations with photoionization modelling to analyze nebular emission, chemical abundances, photon leakage, and star formation rates, revealing discrepancies and effects of dense shells.

Contribution

It introduces a multicomponent photoionization model applied to 2-D chemo-dynamical dwarf galaxy simulations, providing new insights into emission lines, abundance calculations, and photon escape fractions.

Findings

Oxygen abundance estimates vary between methods and simulation data.

The average photon escape fraction is approximately 35-40%.

Halpha-based star formation rates align with true rates only initially.

Abstract

Photoionization modelling allows to follow the transport, the emergence, and the absorption of photons taking into account all important processes in nebular plasmas. Such modelling needs the spatial distribution of density, chemical abundances and temperature, that can be provided by chemo-dynamical simulations (ChDS) of dwarf galaxies. We perform multicomponent photoionization modelling (MPhM) of the ionized gas using 2-D ChDSs of dwarf galaxies. We calculate emissivity maps for important nebular emission lines. Their intensities are used to derive the chemical abundance of oxygen by the so-called Te- and R23-methods. Some disagreements are found between oxygen abundances calculated with these methods and the ones coming from the ChDSs. We investigate the fraction of ionizing radiation emitted in the star-forming region which is able to leak out the galaxy. The time- and direction-averaged escape fraction in our simulation is 0.35-0.4. Finally, we have calculated the total Halpha lumi- nosity of our model galaxy using Kennicutt's calibration to derive the star-formation rate. This value has been compared to the 'true' rate in the ChDSs. The Halpha-based star-formation rate agrees with the true one only at the beginning of the simulation. Minor deviations arise later on and are due in part to the production of high-energy photons in the warm-hot gas, in part to the leakage of energetic photons out of the galaxy. The effect of artificially introduced thin dense shells (with thicknesses smaller than the ChDSs spatial resolution) is investigated, as well.