Ubiquitous [O II] Emission in Quiescent Galaxies at z ≈ 0.85 from the LEGA-C Survey

Maseda, M.V. and Van Der Wel, A. and Franx, M. and Bell, E.F. and Bezanson, R. and Muzzin, A. and Sobral, D. and D'Eugenio, F. and Gallazzi, A. and De Graaff, A. and Leja, J. and Straatman, C. and Whitaker, K.E. and Williams, C.C. and Wu, P.-F. (2021) Ubiquitous [O II] Emission in Quiescent Galaxies at z ≈ 0.85 from the LEGA-C Survey. The Astrophysical Journal, 923 (1). ISSN 0004-637X

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Using deep rest-frame optical spectroscopy from the Large Early Galaxy Astrophysical Census (LEGA-C) survey, conducted using VIMOS on the ESO Very Large Telescope, we search for low-ionization [O ii] λ λ 3726,3729 emission in the spectra of a mass-complete sample of z ≈ 0.85 galaxies. We find that 59% of UVJ-quiescent (i.e., non-star-forming) galaxies in the sample have [O ii] emission detected above our completeness limit of 1.5 Å, and the median-stacked spectrum of the remaining sample also shows [O ii] emission. The overall fraction of sources with [O ii] above our equivalent width limit is comparable to what we find in the low-redshift universe from GAMA and MASSIVE, except perhaps at the highest stellar masses (>1011.5 M o˙). However, stacked spectra for the individual low-equivalent-width systems uniquely indicates ubiquitous [O ii] emission in the higher-z LEGA-C sample, with typical [O ii] luminosities per unit stellar mass that are a factor of ×3 larger than the lower-z GAMA sample. Star formation at higher-z could play a role in producing the [O ii] emission, although it is unlikely to provide the bulk of the ionizing photons. More work is required to fully quantify the contributions of evolved stellar populations or active galactic nuclei to the observed spectra.

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Journal Article
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The Astrophysical Journal
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This is an author-created, un-copyedited version of an article accepted for publication/published in The Astrophysical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi:10.3847/1538-4357/ac2bfe
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01 Mar 2022 14:50
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18 Sep 2023 02:00