Oral Presentation
The role of the galaxy group environment in quenching at high redshifts
Presenter: Takumi Kakimoto (The Graduate University for Advanced Studies)
Recently, we reported on the spectroscopic confirmation of a massive quiescent galaxy (QG) at z=4.53 in the COSMOS field (Kakimoto et al. 2024). This galaxy is among the youngest QGs confirmed so far with a formation redshift of 5.2 (200 Myr old) and is likely a galaxy in the process of being quenched. A unique aspect of the galaxy is that it is in an extremely dense region, suggesting that effects from surrounding environment are important to quench the galaxy. A follow-up spectroscopic observation with FOCAS is scheduled in March 2024 and we will report on results from the observation. To extend this work, we make an attempt to unveil the typical environment of massive QGs at high redshifts. By selecting QGs at z>3 using high-accuracy photometric redshifts, we find that many of them are located in group-like environment. We summarize differences between isolated QGs and those in group environment and discuss their implications for the quenching physics.
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