Stellar Metallicities and Elemental Abundance Ratios of z ∼ 1.4 Massive Quiescent Galaxies

Kriek, Mariska and Price, Sedona H. and Conroy, Charlie and Suess, Katherine A. and Mowla, Lamiya and Pasha, Imad and Bezanson, Rachel and Dokkum, Pieter van and Barro, Guillermo (2019) Stellar Metallicities and Elemental Abundance Ratios of z ∼ 1.4 Massive Quiescent Galaxies. The Astrophysical Journal, 880 (2). L31. ISSN 2041-8213

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Abstract

The chemical composition of galaxies has been measured out to z ∼ 4. However, nearly all studies beyond z ∼ 0.7 are based on strong-line emission from H ii regions within star-forming galaxies. Measuring the chemical composition of distant quiescent galaxies is extremely challenging, as the required stellar absorption features are faint and shifted to near-infrared wavelengths. Here, we present ultradeep rest-frame optical spectra of five massive quiescent galaxies at z ∼ 1.4, all of which show numerous stellar absorption lines. We derive the abundance ratios [Mg/Fe] and [Fe/H] for three out of five galaxies; the remaining two galaxies have too young luminosity-weighted ages to yield robust measurements. Similar to lower-redshift findings, [Mg/Fe] appears positively correlated with stellar mass, while [Fe/H] is approximately constant with mass. These results may imply that the stellar mass–metallicity relation was already in place at z ∼ 1.4. While the [Mg/Fe]−mass relation at z ∼ 1.4 is consistent with the z < 0.7 relation, [Fe/H] at z ∼ 1.4 is ∼0.2 dex lower than at z < 0.7. With a [Mg/Fe] of ${0.44}_{-0.07}^{+0.08}$ the most massive galaxy may be more α-enhanced than similar-mass galaxies at lower redshift, but the offset is less significant than the [Mg/Fe] of 0.6 previously found for a massive galaxy at z = 2.1. Nonetheless, these results combined may suggest that [Mg/Fe] in the most massive galaxies decreases over time, possibly by accreting low-mass, less α-enhanced galaxies. A larger galaxy sample is needed to confirm this scenario. Finally, the abundance ratios indicate short star formation timescales of 0.2–1.0 Gyr.

Item Type: Article
Subjects: STM Open Press > Physics and Astronomy
Depositing User: Unnamed user with email support@stmopenpress.com
Date Deposited: 31 May 2023 06:01
Last Modified: 25 Jul 2024 07:47
URI: http://journal.submissionpages.com/id/eprint/1398

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