The Stellar Metallicities of Massive Quiescent Galaxies at 1.0

Medientyp: E-Artikel
Titel: The Stellar Metallicities of Massive Quiescent Galaxies at 1.0
Beteiligte: Carnall, Adam C.; McLure, Ross J.; Dunlop, James S.; Hamadouche, Massissilia; Cullen, Fergus; McLeod, Derek J.; Begley, Ryan; Amorin, Ricardo; Bolzonella, Micol; Castellano, Marco; Cimatti, Andrea; Fontanot, Fabio; Gargiulo, Adriana; Garilli, Bianca; Mannucci, Filippo; Pentericci, Laura; Talia, Margherita; Zamorani, Giovani; Calabro, Antonello; Cresci, Giovanni; Hathi, Nimish P.
Erschienen: American Astronomical Society, 2022
Erschienen in: The Astrophysical Journal
Sprache: Nicht zu entscheiden
DOI: 10.3847/1538-4357/ac5b62
ISSN: 0004-637X; 1538-4357
Schlagwörter: Space and Planetary Science ; Astronomy and Astrophysics
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Beschreibung: <jats:title>Abstract</jats:title> <jats:p>We present a rest-frame UV–optical (<jats:italic>λ</jats:italic> = 2500–6400 Å) stacked spectrum representative of massive quiescent galaxies at 1.0 < <jats:italic>z</jats:italic> < 1.3 with log(<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) > 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 <jats:sc>Bagpipes</jats:sc> and [Z/H] = 0.04 ± 0.14 with <jats:sc>Alf</jats:sc>, 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 local universe. We measure the alpha enhancement via the magnesium abundance, obtaining [Mg/Fe] = 0.23 ± 0.12, consistent with galaxies of similar mass in the local universe, indicating no evolution in the average alpha enhancement of log(<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) ∼ 11 quiescent galaxies over the last ∼8 Gyr. This suggests the very high alpha enhancements recently reported for several bright <jats:italic>z</jats:italic> ∼ 1–2 quiescent galaxies are due to their extreme masses, log(<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) ≳ 11.5, in accordance with the well-known downsizing trend, rather than being typical of the <jats:italic>z</jats:italic> ≳ 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 <jats:inline-formula> <jats:tex-math> <?CDATA ${2.5}_{-0.4}^{+0.6}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5b62ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> Gyr, corresponding to a formation redshift <jats:inline-formula> <jats:tex-math> <?CDATA ${z}_{\mathrm{form}}={2.4}_{-0.3}^{+0.6}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>form</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5b62ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. Recent studies have obtained varying average formation redshifts for <jats:italic>z</jats:italic> ≳ 1 massive quiescent galaxies, and, as these studies report consistent metallicities, we identify models with different star formation histories as the most likely cause. Larger spectroscopic samples from upcoming ground-based instruments will provide precise constraints on ages and metallicities at <jats:italic>z</jats:italic> ≳ 1. Combining these with precise stellar mass functions for <jats:italic>z</jats:italic> > 2 quiescent galaxies from the James Webb Space Telescope will provide an independent test of formation redshifts derived from spectral fitting.</jats:p>
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