Ubiquitous [OII] Emission in Quiescent Galaxies at z ~ 0.85

Maseda, Michael V. and Wel, Arjen van der and Franx, Marijn and Bell, Eric F. and Bezanson, Rachel and Muzzin, Adam and Sobral, David and D'Eugenio, Francesco and Gallazzi, Anna and Graaff, Anna de and Leja, Joel and Straatman, Caroline and Whitaker, Katherine E. and Williams, Christina C. and Wu, Po-Feng (2021) Ubiquitous [OII] Emission in Quiescent Galaxies at z ~ 0.85. The Astrophysical Journal. ISSN 0004-637X (In Press)

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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 systematically search for low-ionization [OII] 3726,3729 emission in the spectra of a mass-complete sample of z~0.85 galaxies. Intriguingly, we find that 59 percent of UVJ-quiescent (i.e. non star-forming) galaxies in the sample have ionized gas, as traced by [OII] emission, detected above our completeness limit of 1.5 Angstroms. The median stacked spectrum of the lowest equivalent width quiescent galaxies also shows [OII] emission. The overall fraction of sources with [OII] 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 (log Mstar/Msol > 11.5). However, stacked spectra for the individual low-equivalent width systems uniquely indicates ubiquitous [OII] emission in the higher-z LEGA-C sample, with typical [OII] luminosities per unit stellar mass that are a factor of 3 larger than the lower-z GAMA sample. Star formation in these otherwise quiescent galaxies could play a role in producing the [OII] emission at higher-z, 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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08 Nov 2021 13:00
In Press
Last Modified:
26 Jan 2022 12:40