Line Emission From Radiation-Pressurized H Ii Regions. Ii. Dynamics and Population Synthesis

Abstract

Optical and infrared emission lines from H II 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 H II 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 H II region line emission depends on the physics of winds and radiation pressure. In a companion paper we construct models of single H II 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 H II 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 H II regions within them.

A Universal Density Structure for Circumgalactic Gas

“…RPC conditions have been shown to apply in at least some star forming regions (Draine 2011;Yeh & Matzner 2012;Yeh et al 2013;Verdolini et al 2013), in AGN emission line regions (Dopita et al 2002;Baskin et al 2014a;Stern et al 2014aStern et al , 2016, in AGN absorption line regions Baskin et al 2014b), and possibly in the CGM of quasar hosts, in the part exposed to the quasar radiation (Arrigoni Battaia et al 2016). Assuming that dust grains are embedded in the CGM gas, as suggested by the results of Ménard et al (2010), then the dominant contribution to the integral in eqn.…”

SLUG – stochastically lighting up galaxies – III. A suite of tools for simulated photometry, spectroscopy, and Bayesian inference with stochastic stellar populations

“…The major limitations of the built-in approach are: (1) because slug's built-in calculation relies on pre-tabulated values for the metal line emission and assumes either a constant or a similarly pre-tabulated temperature (which significantly affects the continuum emission), it misses the variation in emission caused by the fact that H ii regions exist at a range of densities and ionization parameters, which in turn induces substantial variations in their nebular emission (e.g. Yeh et al 2013;Verdolini et al 2013);…”

“…In the cluster case, the H ii regions need not all have the same density or radius; indeed, one would expect a range of both properties to be present, since not all star clusters have the same age or ionizing luminosity. We handle this case using a simplified version of the H ii population synthesis model introduced by Verdolini et al (2013) and Yeh et al (2013). The free parameters to be specified in this model are the chemical composition and the density in the 4 These filters were downloaded from http://www.…”

Bottling the Champagne: Dynamics and Radiation Trapping of Wind-Driven Bubbles around Massive Stars

“…In the model of Pellegrini et al (2007), which includes an extended wind bubble, radiation pressure further reduces the efficiency of photoionisation feedback by pushing the ionised gas into a thinner shell, where it recombines faster. This analysis has been further applied to observed feedback structures around massive stars and clusters with an embedded wind bubble in Pellegrini et al (2009), Yeh & Matzner (2012), Verdolini et al (2013), Rahner et al (2017 and Pellegrini et al (2020).…”