Brian Welch: Exploring the distant universe at small scales with gravitational lensing

Tuesday 2 Jun 2026, 13:15 → 14:00 Europe/Stockholm

FB54 (AlbaNova Main Building)

The Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) together offer an unprecedentedly detailed view of galaxies across cosmic time, from the first few hundred million years after the Big Bang through today. However, even these powerful telescopes struggle to resolve the small-scale building blocks of galaxies in the distant universe. Gravitational lensing provides an extra boost to the resolving power of HST and JWST, using massive galaxy clusters in the foreground as cosmic telescopes to magnify distant galaxies. In this talk, I will discuss how the combination of HST, JWST, and gravitational lensing provides a window into the heart of distant galaxies, revealing compact star clusters that are key engines of evolution within galaxies. I will highlight how lensed galaxies provide a unique view of star formation and quenching within galaxies, allowing us to see both actively star-forming regions and quiescent regions side-by-side in galaxies in the distant universe. And I will discuss how lensed galaxies allow us to pinpoint the stellar populations driving chemical evolution in galaxies, connecting young massive star clusters with the abundances of elements in their surrounding HII regions.

About the speaker: Currently I am a research fellow at the International Space Science Institute (ISSI) in Bern, Switzerland. When I'm not doing science, I enjoy exploring the mountains of Switzerland on skis, bike, or by foot depending on the season.
Before starting at ISSI, I was a postdoctoral researcher employed by the University of Maryland, College Park, working at NASA Goddard Space Flight Center through the CRESST II cooperative agreement.
I did my PhD at Johns Hopkins University, working with both Dan Coe (at the Space Telescope Science Institute, across the street from JHU), and Stephan McCandliss. My PhD primarily focused on exploring the small-scale details of distant galaxies using the combined power of the Hubble Space Telescope and gravitational lensing, but in the early years I also dabbled in launching sub-orbital sounding rockets.
Prior to starting at JHU, I got my B.A. in Physics at the University of Chicago.

In the OKC: AlbaNova C6:3025