0 Assigned ID: 4314 ----- Attempting Submission 1 (Wed May 24 13:02:31 GMT 2023) ----- HST Phase I Proposal 4314 successfully submitted. Receipt: # 4314-1 ----- Attempting Submission 2 (Wed May 24 18:34:01 GMT 2023) ----- Many dwarf galaxies appear to have "outside-in" age gradients, with the oldest stellar populations extending to the largest radii and younger stellar populations in the centers. In this proposal, we use the largest-ever simulated sample of dwarf galaxies to study the origin of age gradients in dwarfs across a range of mass, morphology, and environment. We demonstrate that the simulations reproduce observed age gradients in dwarf galaxies, and that they produce a diverse range of morphologies as a function of mass, as well as the observed trend in size-luminosity. We have identified a clear signature of age gradient variation as a function of star formation history. This signature is already being tested by archival HST resolved star observations. We will identify both the formation radius and final radius of every star particle, and disentangle re-shuffling of stars due to, e.g., mergers vs feedback mechanisms. A direct test of the theoretical age gradients against existing HST data has the potential to be a critical test of feedback, including the strength of the feedback model between different galaxy formation simulations. Thus, this theory work will both advance our understanding of the formation of observed dwarf galaxies, and a comparison against HST data will work to constrain galaxy formation models. Alyson Brooks (PI) and Ferah Munshi (co-I) have over a decade of experience simulating and analyzing dwarf galaxies. They are experts in interpreting observations using fully cosmological simulations. Brooks has successfully led three prior HST theory proposals. Ryan Leaman and Kristy McQuinn are observers with experience in analyzing the star formation histories of dwarf galaxies using resolved stars, including age gradients in dwarf galaxies. Roger Cohen is the PI of AR-17038, which is investigating the age gradients in galaxies in the HST archive. McQuinn is also a co-I on AR-17038. We will work closely with the archival investigators to determine whether the trends predicted in simulations are recoverable in the archival data. Stellar Populations and the Interstellar Medium Galaxies 0 Regular false false false true false false SUPPORTED