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

Aims. We analyzed the sizes and star formation histories (SFHs) of 2908 galaxies with M★ ≥ 109 M⊙ at 0.6 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 (τq). The main quiescent population quenched over τq = 1.23 ± 0.04 Gyr, whereas the compact post-starburst galaxies (PSBs) quenched much faster, τq = 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 (zform ∼ 1.9) and quenched on the shortest timescales. The general trends with galaxy size, Z★, and zform 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.