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 provided the ionizing photons that drove cosmic reionization. Yet, theoretical models of such stars have never been confronted with data because they are very challenging to observe. I'm leading programs on the Hubble and Keck telescopes to observe O stars in nearby, low-metallicity galaxies. These data have already revealed weak stellar winds and fast rotation in the lowest-metallicity stars and provided the first-ever empirical constraints on a metal-poor O star's ionizing spectrum.

Star formation in extremely low-metallicity environments

How the first stars formed from gas not yet polluted by metals remains mysterious, and has important implications for how quickly early galaxies built up their mass. While cold molecular gas is required to fuel star formation in metal-rich galaxies, some models predict that stars can form directly from atomic gas at very low metallicity. I am the PI of JWST Cycle 2 program GO-3449 to search for emission from warm molecular hydrogen in the extremely metal-poor, star-forming galaxy Leo P. A detection or strict upper limit on the molecular gas content will provide an important 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 a leader in the GLOW (Galaxies Losing Oxygen via Winds) collaboration (AR-16144; PI: K. McQuinn), which is measuring the fraction of metals lost from low-mass galaxies as a benchmark for stellar feedback models.

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).