Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: IV The Controlling Parameters of the Starburst SED

TL;DR

This paper develops advanced models of starburst galaxy spectral energy distributions by integrating stellar, nebular, and dynamical models, introducing a compactness parameter that influences dust emission and analyzing metallicity effects.

Contribution

It introduces a new compactness parameter controlling the far-IR dust emission shape and provides comprehensive templates for different stellar and dust components in starburst galaxies.

Findings

The compactness parameter effectively controls the dust emission peak.

Models successfully fit observed SEDs of starburst galaxies from UV to mm wavelengths.

Metallicity impacts PAH feature strength and overall SED shape.

Abstract

We combine the the stellar spectral synthesis code Starburst99, the nebular modelling code MAPPINGSIII, and a 1-D dynamical evolution model of HII regions around massive clusters of young stars to generate improved models of the spectral energy distribution (SED) of starburst galaxies. We introduce a compactness parameter, C, which characterizes the specific intensity of the radiation field at ionization fronts in HII regions, and which controls the shape of the far-IR dust re-emission, often referred to loosely as the dust ``temperature''. We also investigate the effect of metallicity on the overall SED and in particular, on the strength of the PAH features. We provide templates for the mean emission produced by the young compact HII regions, the older (10 - 100 Myr) stars and for the wavelength-dependent attenuation produced by a foreground screen of the dust used in our model. We demonstrate that these components may be combined to produce a excellent fit to the observed SEDs of star formation dominated galaxies which are often used as templates (Arp 220 and NGC 6240). This fit extends from the Lyman Limit to wavelengths of about one mm. The methods presented in both this paper and in the previous papers of this series allow the extraction of the physical parameters of the starburst region (star formation rates, star formation rate history, mean cluster mass, metallicity, dust attenuation and pressure) from the analysis of the pan-spectral SED.