WARPFIELD-EMP: The Self-Consistent Prediction of Emission Lines from Evolving HII Regions in Dense Molecular Clouds

TL;DR

This paper introduces warpfield-emp, a comprehensive model coupling stellar feedback, radiative transfer, and emission predictions to analyze evolving HII regions in dense molecular clouds, validated against observations.

Contribution

The paper presents warpfield-emp, a novel, fast, self-consistent model that predicts emission lines from evolving HII regions, incorporating multiple physical processes and avoiding degeneracies in diagnostics.

Findings

Good agreement with SITELLE observations of NGC 628 HII regions.

Modeling from first principles helps relate diagnostics to physical parameters.

Insights into metallicity diagnostics and cluster evolution.

Abstract

We present the {\sc warpfield} emission predictor, {\sc warpfield-emp}, which couples the 1D stellar feedback code {\sc warpfield} with the {\sc cloudy} \hii region/PDR code and the {\sc polaris} radiative transfer code, in order to make detailed predictions for the time-dependent line and continuum emission arising from the H{\sc ii} region and PDR surrounding an evolving star cluster. {\sc warpfield-emp} accounts for a wide range of physical processes (stellar winds, supernovae, radiation pressure, gravity, thermal conduction, radiative cooling, dust extinction etc.) and yet runs quickly enough to allow us to explore broad ranges of different cloud parameters. We compare the results of an extensive set of models with SITELLE observations of a large sample of \hii regions in NGC~628 and find very good agreement, particularly for the highest signal-to-noise observations. We show that our approach of modeling individual clouds from first principles (instead of in terms of dimensionless quantities such as the ionization parameter) allows us to avoid long-standing degeneracies in the interpretation of \hii region diagnostics and enables us to relate these diagnostics to important physical parameters such as cloud mass or cluster age. Finally, we explore the implications of our models regarding the reliability of simple metallicity diagnostics, the properties of long-lived embedded clusters, and the role played by winds and supernovae in regulating \hii region and PDR line emission.