The decline of star formation in galaxies is called quenching, and the specific physical mechanism of quenching is unclear. Recently-quenched galaxies(RQGs) can deliver information from center of quenching process, but their short lifespan hampers systematic analysis. With abundant photometric data in the COSMOS field, we use the rest-frame UVJ diagram for the first time to select RQG candidates in 17 clusters at 0.5<z<1.0 and study their stellar mass and environment dependence. This program will be expanded to the whole HSC Deep fields at 0.5 < z < 2.0 soon, and with PFS follow-up spectroscopy in 1-2 yrs. Here we request a pilot program to obtain deep spectra of all 64 RQG candidates in 2 clusters. We aim to spectroscopically confirm our RQGs to determine quenching’s dependence on mass and environment. Spectroscopy and photometry fitting will allow us to estimate star formation history and quenching timescale, hence breaking the degeneracy between visibility time and quenching properties in current analysis. Adding spectroscopic data to current photometric information, we will be able to understand quenching mechanisms of our targets. Note also that it’s essential for PI’s PhD thesis to be completed in 2023 before start of PFS operation.
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