Linking stellar populations to HII regions across nearby galaxies: I. Constraining pre-supernova feedback from young clusters in NGC1672

TL;DR

This study investigates the relative roles of different stellar feedback mechanisms in shaping HII regions in NGC 1672, using high-resolution imaging and spectroscopic data to quantify pressures and their dependence on region properties.

Contribution

It provides new observational constraints on the importance of radiation, wind, and thermal pressures in HII region evolution, highlighting the dominant role of radiation pressure in these environments.

Findings

Radiation pressure contributes more to total pressure than previously thought.

Higher pressures are found in more compact HII regions.

Pressure contributions vary with stellar population properties.

Abstract

One of the fundamental factors regulating the evolution of galaxies is stellar feedback. However, we still do not have strong observational constraints on the relative importance of the different feedback mechanisms (e.g. radiation, ionised gas pressure, stellar winds) in driving HII region evolution and molecular cloud disruption. In this letter, we constrain the relative importance of the various feedback mechanisms from young massive star populations by resolving HII regions across the disk of the nearby star-forming galaxy NGC 1672. We combine measurements of ionised gas nebular lines obtained by PHANGS-MUSE, with high-resolution imaging from the HST in both the narrow-band H{\alpha} and broad-band filters. We identify a sample of 40 isolated, compact HII regions in the HST H{\alpha} image, for which we measure the sizes that were previously unresolved in seeing-limited ground-based observations. Additionally, we identify the ionisation source(s) for each HII region from catalogues produced as part of the PHANGS-HST survey. We find that the HII regions investigated are mildly dominated by thermal or wind pressure, yet their elevation above the radiation pressure is within the expected uncertainty range. We see that radiation pressure provides a substantially higher contribution to the total pressure than previously found in the literature over similar size scales. In general, we find higher pressures within more compact HII regions, which is driven by the inherent size scaling relations of each pressure term, albeit with significant scatter introduced by the variation in the stellar population properties (e.g. luminosity, mass, age, metallicity). For nearby galaxies, here we provide a promising approach that could yield the statistics required to map out how the importance of different stellar feedback mechanisms evolve over the lifetime of an HII region.