Martha Boyer (STScI)

Deciphering the Effect of AGB Stars on Galaxies

Thermally-pulsing Asymptotic Giant Branch (TP-AGB) stars dominate the IR flux in star-forming galaxies (up to 70%). This dominance has a
significant impact on model-dependent derived galaxy properties like the star-formation rate and stellar mass, yet the stellar models that
yield these results are not able to reproduce TP-AGB observed properties. IR data are essential for calibrating TP-AGB models. HST's
medium-band IR filters are uniquely suited for TP-AGB observations and have enabled the first TP-AGB calibration observations in galaxies
beyond the Milky Way system. This capability significantly broadens the metallicity and age baselines for model calibrations, making them
far more broadly applicable than what has been provided by the typically-used Magellanic Clouds. I will present results using these
HST filters to identify TP-AGB stars in M31 and other nearby galaxies and discuss JWST Cycle 1 programs that will quantify the TP-AGB dust
production and mass loss, providing stringent constraints on TP-AGB lifetimes at low metallicity.