Oral Presentation

Revealing impacts of stellar mass and environment on galaxy quenching since z~1

Author(s): Zhiying MAO (Tohoku University)

Presenter: Zhiying Mao (Tohoku University)

Galaxy quenching is an important step in galaxy evolution. To understand quenching process, a key population, recently-quenched galaxy (RQG) can reveal the scenario of galaxies undergoing quenching process. Using multi-band photometric data in COSMOS2015 catalog and rest-frame UVJ selection which is confirmed by DEIMOS spectra, we are able to separate a relatively reliable and large sample of RQGs at z~0.5-1.0. These RQGs are selected from 14 clusters in COSMOS field to better analyse the impact of environment.
We use ratio of N(RQG)/N(star-forming galaxy) and N(RQG)/N(quiescent galaxy) to show quenching efficiency and stage of quenching respectively. We confirmed the downsizing scenario and found the environmental effects are more effective for low mass galaxies. What is unique for our study is that we use model evolutionary tracks on UVJ diagram to separate galaxies go through short and long timescale quenching. We found massive galaxies in cluster outskirts tend to have longer quenching timescale, while low-mass galaxies in cluster centre tend to quench faster. This is consistent with the scenario that quenching of outskirt massive galaxies is dominated by AGN feedback and quenching of low mass central galaxies is dominated by ram pressure stripping.
In the future, we wish to take advantage of PFS' large FOV and high efficiency to obtain spectra of this relatively complete RQG sample. At that time we will be able to do more detailed analysis of quenching mechanisms.