Chemical Abundances of Early Quiescent Galaxies: New Observations and Modelling Impacts

Recent stellar chemical abundance measurements of a handful of z2 quiescent galaxies have suggested these galaxies exhibit a remarkably strong -enhancement compared to their local and intermediate redshift counterparts. This apparent chemical evolution following quenching suggests that even the innermost regions of massive early-type galaxies may have experienced substantial mixing of stars in mergers, challenging a purely inside-out growth model. However, larger samples are needed to determine whether a high -enhancement (Mg/Fe 0. 5) is common in z 2 quiescent galaxies, and a comparative analysis is needed to determine whether it is consistently inferred using different stellar population synthesis models. We report age and stellar chemical abundance measurements for a sample of four gravitationally lensed quiescent galaxies at z2. 1-2. 65 based on Magellan/FIRE spectroscopy. For three of these galaxies we constrain the -enhancement, and in two cases we measure high values comparable to earlier results when the spectra are analyzed consistently. We also find that the choice of modeling approach can exert a significant effect on the measured abundances. This model dependence can be partly, but not entirely, explained by the complex abundance patterns of elements in galaxies, which has been observed at lower redshifts and in one z 2 quiescent galaxy. Our investigation highlights the importance of independently varying abundance of elements when fitting the spectra of such galaxies. Observations with JWST will soon deliver precise and spatially resolved abundances of these and other quiescent galaxies at cosmic noon, opening a new window into their evolution.