2023/08/07 by Bevacqua, Davide, Saracco, Paolo, La Barbera, Francesco +6 · 1 citation
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2308.03441
We measure the [α/Fe] abundances for 183 quiescent galaxies at z = 0.60 - 0.75 with stellar masses ranging 10.4 ≤ log10 10.4 ≤ log10 (M_* /M_\odot) ≤ 11.6 selected from the LEGA-C survey. We estimate [α/Fe] from the ratio of the spectral indices Mgb (λ ∼ 5177 Å) and Fe4383, compared to predictions of simple stellar population models. We find that 91% of quiescents in our sample have supersolar [α/Fe], with an average value of [α/Fe] = +0.24 ± 0.01. We find no significant correlation between [α/Fe] and stellar metallicity, mass, velocity dispersion, and average formation time. Galaxies that formed the bulk of their stellar mass on time scales shorter than 1 Gyr follow the same [α/Fe] distribution as those which formed on longer time scales. In comparison to local early-type galaxies and to stacked spectra of quiescent galaxies at z = 0.38 and z = 0.07, we find that the average [α/Fe] has not changed between z = 0.75 and the present time. Our work shows that the vast majority of massive quiescent galaxies at z ∼ 0.7 are α-enhanced, and that no detectable evolution of the average [α/Fe] has taken place over the last ∼ 6.5 Gyr.