Cake Talk by Kei Ito
Some massive galaxies are now known to stop their star formation, even just 1-2 Gyrs from the Big Bang. Their quenching mechanisms are observationally still in the mystery, and AGNs or environments are expected to have their role according to the simulations. JWST spectroscopy now enables us to investigate such early quiescent galaxies in more detail than ever regarding these aspects. In this talk, I will introduce our studies to characterize massive quiescent galaxies using JWST/NIRSpec spectra. Specifically, I will report two case studies. In the first study, we found a quiescent galaxy at z=2.1 having a broad Halpha emission line, which is likely from its AGN. We derived its black hole mass through its flux and width and discussed the location of quiescent galaxies at z>=2 in the black hole mass v.s. Stellar velocity dispersion relation. In the second study, we spectroscopically confirmed a very close (~4.5 kpc) pair of quiescent galaxies at z=3.44. Comparing it with various simulations, we have argued that this pair is highly expected to get merged by z~0. Since this is located in the center of the large-scale structure called the Cosmic Vine, this pair is likely to become a brightest cluster galaxy in the local Universe.