The LEGA-C galaxy survey: Multiple quenching channels for quiescent galaxies at z ∼ 1

¹ STAR Institute, Université de Liège, Quartier Agora Allée du six Aout 19c B-4000 Liege, Belgium
² Sterrenkundig Observatorium Universiteit Gent Krijgslaan 281 S9 B-9000 Gent, Belgium
³ Department of Physics and Astronomy and PITT PACC, University of Pittsburgh Pittsburgh PA 15260, USA
⁴ Max-Planck Institut für Astronomie Königstuhl D-69117 Heidelberg, Germany
⁵ Institute of Astrophysics, National Taiwan University Taipei 10617, Taiwan
⁶ Department of Physics and Center for Theoretical Physics, National Taiwan University Taipei 10617, Taiwan
⁷ Physics Division, National Center for Theoretical Sciences Taipei 10617, Taiwan
⁸ Department of Astronomy, University of Michigan 1085 South University Avenue Ann Arbor MI 48109, USA
⁹ Kavli Institute for Cosmology, University of Cambridge, Madingley Road Cambridge CB3 0HA, UK
¹⁰ Cavendish Laboratory – Astrophysics Group, University of Cambridge 19 JJ Thomson Avenue Cambridge CB3 0HE, UK
¹¹ Osservatorio Astrofisico di Arcetri Largo Enrico Fermi 5 I-50125 Firenze, Italy
¹² Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University University Park PA 16802, USA
¹³ Institute for Gravitation and the Cosmos, The Pennsylvania State University University Park PA 16802, USA
¹⁴ Institute for Computational and Data Sciences, The Pennsylvania State University University Park PA 16802, USA

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Received: 17 September 2025
Accepted: 9 December 2025

Abstract

Aims. We analyzed the sizes and star formation histories (SFHs) of 2908 galaxies with M_★ ≥ 10⁹ M_⊙ at 0.6 < z < 1.0, drawn from the Large Early Galaxy Astrophysics Census (LEGA-C) survey. The goal is to investigate the connection between galaxy sizes with SFH, stellar age, and metallicity.

Methods. The SFHs were derived with Prospector by fitting the high signal-to-noise ratio, high spectral resolution spectroscopy drawn from the LEGA-C DR3 together with the broadband photometry from the UltraVISTA catalog. The galaxy sizes were measured by fitting a 2D Sérsic profile to the HST ACS F814W images.

Results. We find diverse SFHs and quenching timescales (τ_q). The main quiescent population quenched over τ_q = 1.23 ± 0.04 Gyr, whereas the compact post-starburst galaxies (PSBs) quenched much faster, τ_q = 0.13 ± 0.03 Gyr. At fixed stellar mass, smaller quiescent galaxies quenched more rapidly than larger ones; at fixed size, the dependence on stellar mass is weak. Larger quiescent galaxies are marginally younger, quenched more slowly, and have near-solar metallicities, while compact quiescent galaxies are older, metal-rich, and quenched faster. PSBs formed half their mass later (z_form ∼ 1.9) and quenched on the shortest timescales. The general trends with galaxy size, Z_★, and z_form for the quiescent populations remain consistent regardless of the method used to derive the stellar properties.

Conclusions. We conclude that compact quiescent galaxies are consistent with both early moderately fast quenching and with more rapid late quenching. While this may suggest the existence of multiple quenching channels, our data are also compatible with a continuous distribution of quenching timescales. These findings suggest that different physical mechanisms may drive quenching across galaxy populations, potentially leading to similar morphological outcomes despite the differing evolutionary histories.