I use observations of spatially resolved stars and gas in nearby galaxies to study the processes that regulate galaxy evolution.

Ph.D. University of Washington (2019)
B.S. University of Pittsburgh (2013)

Research Program

I work with spectroscopy and imaging across the electromagnetic spectrum from both ground- and space-based telescopes. I use a variety of techniques to address fundamental questions about the connection between massive stars and the gas in their host galaxies, particularly at the low metallicities typical of both nearby, low-mass galaxies and galaxies in the early universe that are too distant to study in detail.

Very Metal-Poor O Stars in Nearby Low-Mass Galaxies as Analogs of the Sources of Cosmic Reionization

Hot, massive, and short-lived O-type stars in the chemically pristine first galaxies likely drove cosmic reionization and their host galaxies' evolution. Yet, theoretical models of such stars have never been confronted with data because they are very challenging to observe. My new Hubble and Keck observations of O stars in nearby, low-metallicity galaxies have already revealed very weak stellar winds, and I am now building on this work with the TEMPOS HST Large Treasury Program to produce a public FUV and optical spectral atlas to anchor models of metal-poor O stars.

Molecular gas in metal-poor, star-forming galaxies

How early stars formed from very low-metallicity gas remains mysterious, and has important implications for the assembly of high-redshift galaxies. While cold molecular gas fuels star formation in metal-rich galaxies, the situation is far from clear at very low metallicity: molecular gas could be less important than atomic gas for star formation in this regime, and it is also challenging to observe. My Cycle 2 JWST program detected molecular hydrogen in the extremely metal-poor galaxy Leo P, confirming that such galaxies can form substantial molecular gas and providing a new anchor for star-formation physics in early galaxies.

The connection between starbursts and the dynamical and chemical evolution of low-mass galaxies

Low-mass galaxies oscillate between periods of vigorous star formation and quiescence. Energetic feedback from massive stars formed during starbursts drives gas out of the host galaxies' shallow potential wells, redistributing mass and removing newly formed metals. I am the PI of HST program AR-16155 to test the prediction that this mechanism can form the "cored" dark matter profiles observed in the centers of low-mass galaxies. I'm also heavily involved in ongoing efforts to constrain stellar feedback by measuring the radial age gradients (Cohen+ in prep) and fraction of metals lost (McQuinn+ in prep) from low-mass galaxies.

Decoding feedback from stars and AGN via the metal content of massive galaxies and their CGM

Despite their deeper gravitational potential wells, massive spiral galaxies like our Milky Way are also shaped by feedback from both stars and accreting supermassive black holes (AGN) at their centers. I demonstrated that the nearby Andromeda galaxy has lost most of the metals formed by its stars and found novel signatures of recent, outward metal transport that hint at a galactic fountain. Recently, I collaborated with galaxy formation simulators to study the importance of black-hole vs. stellar feedback. We showed that more massive black holes can effectively drive metals out of galaxies and into the circumgalactic medium (CGM).