Misc,
Line Emission from Radiation-Pressurized HII Region II: Dynamics and Population Synthesis
(2013)cite arxiv:1303.4737Comment: 12 pages, 11 figures, accepted for publication in ApJ.
Abstract
Optical and infrared emission lines from HII regions are an important
diagnostic used to study galaxies, but interpretation of these lines requires
significant modeling of both the internal structure and dynamical evolution of
the emitting regions. Most of the models in common use today assume that HII
region dynamics are dominated by the expansion of stellar wind bubbles, and
have neglected the contribution of radiation pressure to the dynamics, and in
some cases also to the internal structure. However, recent observations of
nearby galaxies suggest that neither assumption is justified, motivating us to
revisit the question of how HII region line emission depends on the physics of
winds and radiation pressure. In a companion paper we construct models of
single HII regions including and excluding radiation pressure and winds, and in
this paper we describe a population synthesis code that uses these models to
simulate galactic collections of HII regions with varying physical parameters.
We show that the choice of physical parameters has significant effects on
galactic emission line ratios, and that in some cases the line ratios can
exceed previously claimed theoretical limits. Our results suggest that the
recently-reported offset in line ratio values between high-redshift
star-forming galaxies and those in the local universe may be partially
explained by the presence of large numbers of radiation pressured-dominated HII
regions within them.
