Ashley T. Barnes

My role in PHANGS: Observations of nearby extragalactic systems offer us a unique top-down view of feedback systems across entire galaxy discs, not possible within the Milky Way. In a recent paper, Barnes et PHANGS (2021b; subm), we investigate the role of early stellar feedback within a sample of HII regions identified across 19 nearby spiral galaxies (Figure 1). This work exploits observations from VLT/MUSE, ALMA, and HST(and soon JWST) observations (Emsellem et PHANGS, 2021; Lee et PHANGS, 2021; Leroy et PHANGS, 2021). We identified around 6000 HII regions for which I determined the physical properties and feedback mechanisms (i.e. radiation pressure, stellar winds, and thermal); increasing the number of similar measurements available within the literature by ×100. I found that the largest HII regions are driven by the thermal pressure of the photoionised gas, and that the majority of these HII regions are over-pressured with respect to their immediate environment. Yet, there is a small sample of compact HII regions that are underpressured, which mostly reside in galaxy centres. Highlighting that the feedback efficiency may be limited within extreme, highly pressured environments (also see Barnes et al. 2020b).