Magnified studies of distant galaxies are becoming a powerful way to understand the astrophysical processes that are responsible for understanding how the stars and galaxies that we observe in the Universe were formed. In the distant universe we have, historically, studied star and galaxy formation galaxy-by-galaxy, because most of our observational facilities can only marginally resolve structures smaller than the typical size of a galaxy (~1000 parsecs). However, the fundamental unit of star formation in the universe is not a star, nor a galaxy, but rather a star forming region with a typical scale of order ~10s to 100’s of parsecs. We can only resolve the relevant physical scales in distant galaxies that are magnified by natural telescopes. A major focus of my research group at UC is use strong lensing systems to study the signatures of star-formation on the relevant physical scales and constrain the astrophysical processes that explain how galaxies have formed their stars across cosmic time. We use observations from the best ground- and space-based telescopes available (including the James Webb Space Telescope, the Hubble Space Telescope, the Chandra X-ray Observatory, and JWST) to measure the internal properties of star-forming galaxies, as described in more detail below and in my accompanying teaching statement.

Example papers: Wuyts+2012, Bayliss+2014b, Rigby+2015, Bayliss+2017, Johnson+2017, Rigby+2018, Rivera-Thorsen+2019, Bayliss+2020, Kim+2023b

Currently working on this: Josh Roberson, Riley Owens

From Bayliss et al. (2020). We measured spatially resolved emission from high mass X-ray binaries (HMBXs) at Cosmic Noon, opening up a new window into high energy studies of resolved, distant star-forming regions.

From Rivera-Thorsen et al. (2019), Kim et al. (2023b), and Owens et al. (2024, submitted). We have been centrally involved in the discovery and characterization of the Sunburst Arc, a strongly lensed LyC leaking galaxy that is a unique laboratory for exploring the physical scale and conditions associated with the highly anisotropic escape of ionizing radiation from a typical UV-bright star-forming galaxy.

The broadest goal of observational cosmology is to understand the structure, composition, and physical laws that make up the observable universe. A major challenge is measuring how the main constituents of the universe – normal/baryonic matter, dark matter, and dark energy – form large, gravitationally bound structures, the largest of which are galaxy clusters. Measuring the properties of galaxy clusters is an effective way to test cosmological theories of structure formation, but we are limited in our ability to directly measure quantities like mass, which typically have to be inferred from observations of electromagnetic radiation. Gravitational lensing provides a work-around, however, because the lensing effect directly constraints the amount of matter in a gravitational lens, as well as how that matter is distributed. We use systems with well-constrained gravitational lensing constrains to measure their total lensing masses, and combine that information with other measurements of the total baryonic and stellar mass components. Ongoing work by students in my group uses large ground-based telescopes along with Hubble and Chandra to measure the mass distributions within massive galaxy clusters that act as strong lenses and compare those measurements to predictions from leading cosmological models of structure formation. 

Example papers: Bayliss+2011a, Bayliss2012, Oguri+2012, Bayliss+2014a, Bayliss+2015, Sharon+2020

Currently working on this: Raven Gassis, Lauren Elicker, Prasanna Adhikari