Thesis Topic: Blowing Bubbles: Unveiling the Impact of Stellar Feedback in Nearby Galaxies
Thesis Supervisor: Ashley Barnes
Abstract
One of the central challenges in astrophysics is to understand how galaxies grow and form stars, despite containing vast reservoirs of gas that are converted into stars with strikingly low efficiency. The missing ingredient is stellar feedback: the immense energy and momentum injected by massive stars through radiation, winds, and supernovae. Feedback regulates star formation locally by dispersing molecular clouds and driving turbulence, and globally by powering outflows that shape the evolution of entire galaxies. It also sets the conditions for the birth of stars, planetary systems, and, ultimately, habitable environments and life.
The James Webb Space Telescope now reveals galaxies threaded with thousands of feedback-driven superbubbles (NASA press release, ESA image highlights, ESA video), offering an unprecedented opportunity to quantify their impact (see YouTube summary by Watkins et al.). Among these, the 1 kpc-wide “Phantom Void” in NGC 628 stands out as an extreme case, likely excavated by over a thousand supernovae yet still forming stars along its rim (see YouTube summary by Barnes et al.).
This observational PhD project will combine high-resolution, multi-wavelength data from JWST, ALMA (NRAO press release), HST, and VLT/MUSE (ESO press release) to measure gas dispersal, turbulence, and triggered star formation in such structures. Beginning with a detailed case study of the Phantom Void and expanding to a statistical sample across the PHANGS survey, the project will determine how feedback couples to the multi-phase ISM and test whether it suppresses or promotes star formation. Embedded within the PHANGS collaboration, the student will gain early opportunities for impactful publications while pursuing their own interests and ideas, including developing future observing proposals, as part of one of the world’s leading networks in galaxy evolution.
Fig. 1. The nearby “Phantom Galaxy” (NGC 628) as seen with HST and JWST (see Barnes et al. 2023). Left: JWST reveals thousands of feedback-driven superbubbles carved by massive stars. Right: the 1 kpc-wide Phantom Void, likely powered by over a thousand supernovae, dominates the galaxy. The footprint of new JWST spectroscopy is overlaid, enabling studies of how stellar feedback sculpts the interstellar medium and regulates star formation.