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Author ORCID Identifier


Open Access Dissertation

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program


Year Degree Awarded


Month Degree Awarded


First Advisor

Alexandra Pope

Subject Categories

Astrophysics and Astronomy | External Galaxies | Physical Sciences and Mathematics | Stars, Interstellar Medium and the Galaxy


Galaxies in the past were forming more stars than those today, but the driving force behind this increase in activity remains uncertain. In this thesis I explore the origin of high star-formation rates today and in the past by studying the properties of gas and dust in the cold interstellar medium (ISM) of dusty galaxies over cosmic time. Critically, we do not yet understand how these galaxies could form so many stars. This work began with my discovery of unusual infrared (IR) emission line ratios in the class of dusty galaxies where most of the Universe’s stars were formed. To fully understand the source of these unusual emission line ratios, I turn to local analogs of the distant galaxies I study at high-redshift to investigate in detail the ratio of far-IR fine-structure line emission to mid-IR Polycylic Aromatic Hydrocarbons (PAHs). I find that gas within young star-forming regions heats and cools differently when it is compressed to high star-formation rate surface densities. I use radio spectroscopy of CO(1-0) and sub-millimeter dust continuum measurements to test how changes in heating and cooling impact the total gas reservoir, and find more efficient star- formation in compact galaxies at all redshifts. The high star-formation rates of distant galaxies may be sustained by this more efficient mode. With spatially resolved studies, I find the IR properties of star-forming, dusty galaxies to be comparable for fixed IR surface density at low- and high-redshift. Finally, to match the formation of stars with the synchronous growth of supermassive black holes I analyze numerical simulations of galaxy formation to study the radiative feedback of active galactic nuclei on dust. Rapidly accreting supermassive black holes can heat the dust in their host galaxies, powering a significant fraction of the cold dust luminosity and biasing IR-derived star-formation rates if left unaccounted for. With the recent launch of the James Webb Space Telescope, the future of extragalactic infrared observations is wide open and this research provides motivation for the continued study of the cold gas and dust conditions from which new stars form.


Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.