Photoionization analysis of chemodynamical dwarf galaxies simulations

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 T e − and R 23 −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 Hα luminosity 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 Hα -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.

Spatially resolved integral field spectroscopy of the ionized gas in IZw18

“…As far as we know, here we present the first study based on IFS to investigate the spatially resolved physical-chemical properties (e.g., electron temperature, gaseous metal abundances, excitation) and the spatial correlations that may hold for the warm ISM in IZw18. Our integral field unit (IFU) data reveal the spatially resolved ionization structure for the ionized gas of IZw18, which provide useful boundary conditions for photoionization models at the lowest metallicity regime (e.g., Melekh et al 2015). Moreover, taking advantage of the IFU data, we derive the integrated physical-chemical characteristics for selected regions, including the IZw18 integrated spectrum, that can be helpful to interpret highz emission-line galaxies.…”

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

“…Finally, the possible contribution of other processes to the ionisation of the gas mentioned in point ( 5) is hardly quantifiable given the very complex physics that describe them and the difficulty of including them in tuned models and simulations (e.g. Melekh et al 2015;Sander & Hensler 2021). The clumpy structure of the Hα images similar to that observed in other photometric bands sensitive to the young stellar distribution (far-(FUV) and near-ultraviolet (NUV), u band) means that their contribution to the total Hα emission of the Virgo galaxies analysed in this work remains negligible.…”

Star formation at low rates - the impact of lacking massive stars on stellar feedback

“…Moreover, the validity of Hα as SFR proxy must be questioned because of various reasons of stellar feedback. Both seems to be possible, to underestimate (Andrews et al 2013) or to overestimate (Melekh et al 2015) the SFR.…”