Galaxies and Cosmology Seminar

Apr

2026

12:00 pm – 1:00 pm

In Person (view details)

Second Year Research Talk

Description

The Pixel Frontier: Revealing Hidden Galaxies and Mapping Galaxy Growth

The James Webb Space Telescope (JWST) has pushed our frontier for finding and spatially-resolving high redshift galaxies, but challenges have been presented both in methods for robustly selecting high redshift galaxies with overlapping foreground lower-redshift galaxies, and feasibly performing spatially-resolved analyses of galaxy properties over large samples to utilize the wealth of pixel-scale data. With efficient machine learning SED fitting techniques, we create pixel-by-pixel specific star-formation rate (sSFR) maps of 328 massive galaxies (log(Mstar) = 9.5-10.5 solar masses) across cosmic time, which takes on average 0.1 seconds to infer galaxy properties per pixel. This is the first large-scale analysis of resolved star formation galaxy properties using only imaging data that is fully pixel-based. This approach enables our investigation into the following question for our sample at fixed stellar mass: How and where do these galaxies build-up their stellar mass, and what physical processes drive and regulate their growth over cosmic time? We create radial profiles of sSFR from our pixel-based maps and analyze them with respect to redshift and star formation activity. We find strong centrally concentrated star formation at high redshift (z > 3) that reflects the compaction/depletion structural cycle of early stochastic star formation, and the emergence of inside-out growth at z ~ 2-2.5 where galaxy disks are building-up through cosmological accretion. The strength of inside-out profiles increases towards z < 1, especially for quiescent populations. Increased central stellar mass surface density for quiescent galaxies indicates the role of bulge formation in the inside-out quenching process. With the power of JWST and the efficiency of machine learning for large galaxy samples, we extend insights for galaxy stellar mass build-up from pre-JWST spatially-resolved studies to higher redshifts and finer spatial resolution, revealing the physical mechanisms that dominate massive galaxy growth and structure at different eras, out to the early universe.