Do high-redshift quiescent galaxies follow a single quenching pathway?

Massive quiescent galaxies are already observed when the Universe was only a few billion years old, but the routes by which they stopped forming stars remain uncertain.

Recent JWST spectroscopy suggests that rapid quenching was common at cosmic noon, yet not all quiescent galaxies appear to share the same formation history.

Using JWST/NIRSpec PRISM spectra and photometry, this project investigates whether high-redshift quiescent galaxies can be separated into distinct formation and quenching pathways.

• Selected high-redshift quiescent galaxy candidates at 2 ≤ z < 6 from Dawn JWST Archive NIRSpec PRISM spectra using rest-frame color diagnostics and spectral quality cuts.
• Matched PRISM spectra to multi-band photometry through RA/Dec-based catalog matching and jointly fit spectra and photometry with Prospector.
• Modeled galaxies with 14-bin nonparametric star formation histories, including a 10 Myr recent bin to measure short-timescale star formation activity.
• Selected robust quiescent galaxies using sSFR_10Myr ≤ 0.2 / t_univ(z), based on posterior median sSFR values.
• Classified quiescent galaxies into Park-like SFH pathways using t₅₀ and t₉₀: early formed/early quenched, early formed/recently quenched, and recently formed/recently quenched.

The quiescent sample separates into multiple SFH pathways rather than a single evolutionary track. Recently formed/recently quenched galaxies show the shortest mass-assembly timescales, the highest redshifts, and the largest fraction of burst-like systems, consistent with a rapid transition toward quiescence. Early formed/recently quenched galaxies are the most massive and metal-rich subgroup while showing little recent burst activity, suggesting delayed or regulated quenching after extended baryon processing. Early formed/early quenched systems resemble older quiescent remnants but retain broad dust and metallicity scatter. Together, these subgroup-dependent trends in stellar mass, metallicity, dust attenuation, and burst fraction indicate diverse quenching histories and heterogeneous baryonic material evolution among high-redshift quiescent galaxies.