Invited Presentation
[Remote] Rapid quenching of massive quiescent galaxies at cosmic noon.
Presenter: Minjung Park (Harvard University)
The existence of massive quiescent galaxies at high redshifts (z>3) requires intense star formation and rapid quenching. In contrast, quiescent galaxies at low redshifts (z<1) seem to have a broad range of quenching timescales, suggesting multiple quenching mechanisms. The link between these two epochs is not yet well understood. At cosmic noon (z~2), many questions about the quiescent galaxy population remain unanswered: what are the quenching histories and mechanisms, and what are the descendants of the quiescent galaxies at early epochs. We study 16 massive quiescent galaxies at z~2 selected from a mass-selected representative sample of the Blue Jay survey. We reconstruct their star formation histories by fitting spectral energy distribution models to the JWST/NIRSpec R~1000 spectra. We find that massive quiescent galaxies at z~2 can be split into three categories with roughly equal numbers of galaxies according to their SFHs: 1) Relatively old galaxies quenched at early epochs; 2) Galaxies that are rapidly and recently quenched after a flat or bursty formation history (depending on the assumed prior); 3) Galaxies that are rapidly and recently quenched after a major starburst. Most recently quenched galaxies show neutral gas outflows, probed by blueshifted Na D absorption, and ionized gas emission, with line ratios consistent with active galactic nucleus (AGN) diagnostics. This suggests that AGN activity drives multi-phase gas outflows, leading to rapid quenching. The two oldest massive quiescent galaxies in our sample appear to have extremely early formation and quenching (z>6), possibly descendants of early post-starbursts at z>3. These galaxies still show neutral gas reservoirs and low-level star formation, consistent with weak H$\alpha$ emission, perhaps because the ejective AGN feedback that caused rapid quenching has weakened over time.
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