Far-infrared line and dust emission from H II regions and photodissociation regions

TL;DR

This paper models the structure of H II regions and photodissociation regions under different spectral energy distributions, applying the results to interpret Herschel observations of extragalactic FIR emissions.

Contribution

It provides the first intensity ratio diagrams for FIR emissions from H II regions and PDRs, aiding interpretation of Herschel data.

Findings

Predicted FIR intensity ratios match observations of M82.

New diagrams help distinguish contributions of H II regions in FIR emissions.

Self-consistent modeling improves understanding of extragalactic FIR data.

Abstract

We explore the effect of varying the spectral energy distribution of the incident continuum, by simultaneously and self-consistently computing the structure of an H II region and a photodissociation region that are in pressure equilibrium. The results of the calculations are applied to extragalactic observations. The intensity ratio diagrams of far-infrared (FIR) emission for Herschel bands (70, 110, 160, 250, 350, and 500 {\mu}m) and the contribution from H II regions for these specific FIR emissions are presented for the first time. With these diagrams, we compare the predicted FIR continuum intensity ratios of M82 with observations by Herschel.