Comparison of Theoretical Starburst Photoionization Models for Optical Diagnostics

Abstract

We study and compare different examples of stellar evolutionary synthesis input parameters used to produce photoionisation model grids using the mappings v modelling code. The aim of this study is to (a) explore the systematic effects of various stellar evolutionary synthesis model parameters on the interpretation of emission lines in optical strong-line diagnostic diagrams, (b) characterise the combination of parameters able to reproduce the spread of local galaxies located in the star-forming region in the Sloan Digital Sky Survey, and (c) investigate the emission from extremely metal-poor galaxies using photoionisation models. We explore and compare the stellar input ionising spectrum (stellar population synthesis code [Starburst99, SLUG, BPASS], stellar evolutionary tracks, stellar atmospheres, star-formation history, sampling of the initial mass function) as well as parameters intrinsic to the H ii region (metallicity, ionisation parameter, pressure, H ii region boundedness). We also perform a comparison of the photoionisation codes mappings and cloudy. On the variations in the ionising spectrum model parameters, we find that the differences in strong emission-line ratios between varying models for a given input model parameter are small, on average ∼0.1 dex. An average difference of ∼0.1 dex in emission-line ratio is also found between models produced with mappings and cloudy. Large differences between the emission-line ratios are found when comparing intrinsic H ii region parameters. We find that low-metallicity galaxies are better explained by a density-bounded H ii region and higher pressures better encompass the spread of galaxies at high redshift.

Stellar populations and physical properties of starbursts in the Antennae galaxy from self-consistent modelling of MUSE spectra

“…One of the caveats of using the Parsec (or Padova) isochrones for modelling massive stars is that they lack the information on the effective temperature correction needed to model the crucial WR evolutionary phase of massive stars. In the absence of this information, STARBURST99, for example, defaults to using the effective stellar temperature instead, which can lead to several orders of magnitude difference in far-ultraviolet spectra computed using Parsec and Geneva isochrones (D'Agostino et al 2019). Therefore, we calculate an effective temperature correction for WR stars following the prescriptions of Leitherer et al (2014) and Smith et al (2002) to incorporate into our implementation of Parsec isochrones.…”

SDSS IV MaNGA: Metallicity and ionisation parameter in local star-forming galaxies from Bayesian fitting to photoionisation models

“…This approach has the advantage of modelling all the available SEL ratios self-consistently, but is also subject to specific limitations. First, the current generation of photoionisation models are not capable of correctly reproducing all the observable SEL ratios (D'Agostino et al 2019). Second, photoionisation models are based on a large number of simplifying assumptions and it is not guaranteed that the obtained solution is unique and that the real uncertainties are correctly estimated.…”

The KMOS$^{\rm 3D}$ Survey: Investigating the Origin of the Elevated Electron Densities in Star-Forming Galaxies at $1\lesssim{z}\lesssim{3}$

“…Masters et al 2014Masters et al , 2016Jones et al 2015;Shapley et al 2015), elevated electron density and ISM pressure (e.g. Dopita et al 2016;D'Agostino et al 2019), higher ionization parameter (e.g. Kashino et al 2017;Bian et al 2020), an increased contribution from shocks and/or Active Galactic Nuclei (AGN; e.g.…”