0 Assigned ID: 3029 ----- Attempting Submission 1 (Thu Mar 24 18:19:18 GMT 2022) ----- Because of their low masses and ubiquity, dwarf galaxies serve as crucial probes of a variety of astrophysical processes taking place from reionization to the present day. State-of-the-art cosmological simulations make predictions for radial stellar population gradients within dwarf galaxies based on feedback having a dominant role, but these predictions have never been tested. We propose to use archival HST optical imaging for a diverse sample of 36 nearby (<5 Mpc) dwarfs to derive star formation histories from color-magnitude diagrams, spatially resolved within radial annuli for each target galaxy. Unlike integrated light analyses, this will provide radial profiles of star formation rate, age, and metallicity that are directly and quantitatively comparable to the model predictions, posing a sensitive test of star formation and feedback physics. To maximize our science return, these results will be leveraged together with high-resolution maps of neutral hydrogen, structural properties from Spitzer IRAC imaging, and optical integrated light color profiles, all analyzed self-consistently. This multi-wavelength approach, combined with a diverse sample, allows us to test the following predictions: 1) Galaxies with younger median ages have flattened radial gradients of both stellar age and metallicity. 2) The slopes of radial age and metallicity gradients are uncorrelated with mass or gas-phase metallicity, but have a tight, linear correlation with global galaxy median age. 3) Age and metallicity gradients are insensitive to previous interactions since accreted stars are well-mixed, and feedback remains the dominant driver of the gradients. PI Cohen is an expert in ground- and space-based precision photometry of resolved stellar populations in the Local Group and beyond, and has led multiple HST GO programs and multiple papers using the tools and techniques we employ here. CoI McQuinn is a leading expert on dwarf galaxy evolution and observed properties at multiple wavelengths, and has led numerous HST GO and AR programs on this topic. CoI van Zee is an expert on gas dynamics and low mass galaxy formation and evolution and the ISM using multiwavelength observations. CoI Hunter is writing a dissertation on the turbulent ISM of low-mass galaxies ascertained from multi-wavelength observations, and has amassed broad data reduction/analysis experience and led a paper on this topic. CoI Dolphin has developed, tested and released software over the last two decades for both PSF photometry customized for HST imaging, and star formation histories calculated from fits to color-magnitude diagrams, and quantifying their uncertainty from multiple sources, and has an extensive background in nearby galaxies. Stellar Populations and the Interstellar Medium Galaxies 0 Regular false false false false false false SUPPORTED