Stellar Feedback and Resolved Stellar IFU Spectroscopy in the nearby Spiral Galaxy NGC 300

TL;DR

This study uses IFU spectroscopy and HST photometry to identify massive stars and analyze stellar feedback in HII regions of the nearby galaxy NGC 300, revealing insights into feedback mechanisms and star formation.

Contribution

It demonstrates the extraction of individual stellar spectra at 2 Mpc, identifies new O-type and Wolf-Rayet stars, and analyzes feedback effects in extragalactic HII regions.

Findings

Stellar feedback dynamics are dominated by gas pressure and stellar winds.

The total gas mass loading factor exceeds the ionized gas mass loading, indicating early evolutionary stages or multi-phase feedback.

Star formation rate and ionized gas pressure are overestimated when scaled to galactic levels.

Abstract

We present MUSE Integral Field Unit (IFU) observations of five individual HII regions in two giant (>100 pc in radius) star-forming complexes in the low-metallicity ($Z$~0.33 $Z_{\odot}$) nearby (D ~ 2 Mpc) dwarf spiral galaxy NGC 300. We combine the IFU data with high spatial resolution HST photometry to demonstrate the extraction of stellar spectra and the classification of individual stars from ground-based data at the distance of 2 Mpc. For the two star-forming complexes, in which no O-type stars had previously been identified, we find a total of 13 newly identified O-type stars in the mass range 15-50 M$_{\odot}$, as well as 4 Wolf-Rayet stars. We use the derived massive stellar content to analyze the impact of stellar feedback on the HII regions. As already found for HII regions in the Magellanic Clouds, the dynamics of the analyzed NGC 300 HII regions are dominated by a combination of the pressure of the ionized gas and stellar winds. By comparing the derived ionized gas mass loading factors to the total gas mass loading factor across the NGC 300 disk, we find that the latter is an order of magnitude higher, either indicating very early evolutionary stages for these HII regions, or being a direct result of the multi-phase nature of feedback-driven bubbles. Moreover, we analyze the relation between the star formation rate and the pressure of the ionized gas as derived from small (<100 pc) scales, as both quantities are systematically overestimated when derived on galactic scales. With the wealth of ongoing and upcoming IFU instruments and programs, this study serves as a pathfinder for the systematic investigation of resolved stellar feedback in nearby galaxies, and it delivers the necessary analysis tools to enable massive stellar content and feedback studies sampling an unprecedented range of HII region properties across entire galaxies in the nearby Universe.