The stellar metallicities of massive quiescent galaxies at 1.0 < z < 1.3 from KMOS+VANDELS

Adam C. Carnall*, Ross J. McLure, James S. Dunlop, Massissilia Hamadouche, Fergus Cullen, Derek J. McLeod, Ryan Begley, Ricardo Amorin, Micol Bolzonella, Marco Castellano, Andrea Cimatti, Fabio Fontanot, Adriana Gargiulo, Bianca Garilli, Filippo Mannucci, Laura Pentericci, Margherita Talia, Giovani Zamorani, Antonello Calabro, Giovanni CresciNimish P. Hathi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We present a rest-frame UV-optical stacked spectrum representative of massive quiescent galaxies at 1.0<z<1.3 with log(M∗/M⊙)>10.8. The stack is constructed using VANDELS survey data, combined with new KMOS observations. We apply two independent full-spectral-fitting approaches, measuring a total metallicity, [Z/H]=−0.13±0.08 with Bagpipes, and [Z/H]=0.04±0.14 with Alf, a fall of ∼0.2−0.3 dex compared with the local Universe. We also measure an iron abundance, [Fe/H] =−0.18±0.08, a fall of ∼0.15 dex compared with the the local Universe. We measure the alpha enhancement via the magnesium abundance, obtaining [Mg/Fe]=0.23±0.12, consistent with similar-mass galaxies in the local Universe, indicating no evolution in the average alpha enhancement of log(M∗/M⊙)=11 quiescent galaxies over the last ∼8 Gyr. This suggests the very high alpha enhancements recently reported for several bright z∼1−2 quiescent galaxies are due to their extreme masses, log(M∗/M⊙)≳11.5, rather than being typical of the z≳1 population. The metallicity evolution we observe with redshift (falling [Z/H], [Fe/H], constant [Mg/Fe]) is consistent with recent studies. We recover a mean stellar age of 2.5+0.6−0.4 Gyr, corresponding to a formation redshift, zform=2.4+0.6−0.3. Recent studies have obtained varying average formation redshifts for z≳1 massive quiescent galaxies, and, as these studies report consistent metallicities, we identify different star-formation-history models as the most likely cause. Larger spectroscopic samples from upcoming ground-based instruments will provide precise constraints on ages and metallicities at z≳1. Combining these with precise JWST z>2 quiescent-galaxy stellar-mass functions will provide an independent test of formation redshifts derived from spectral fitting.
Original languageEnglish
Pages (from-to)1-12
Number of pages12
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 20 Apr 2022


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