Akiba: On the Hunt for Recoiling Supermassive Black Holes Using Tidal Disruption Events / Hyun: Study of star formation activities of the galaxy clusters sitting in the large scale structure and the study of SMGs in JWST-Time Domain Field

Speaker: Tatsuya Akiba (University of Colorado Boulder) / Minhee Hyun (KIPAC) In Person and zoom

Zoom info: https://stanford.zoom.us/j/98604058568

Akiba: Following the merger of two supermassive black holes (SMBHs), a gravitational wave recoil kick is imparted on the merger remnant due to the anisotropic emission of gravitational waves. These recoil kicks can be as high as ~10^3 km/s which exceeds the escape velocity of most galaxies, and these super-kicks can lead to ejected or rogue SMBHs. While there are several candidates, recoiling SMBHs are difficult to uniquely identify since observations so far cannot rule out alternate possibilities such as dual active galactic nuclei. Here, we present a novel observational signature: off-nuclear or extragalactic tidal disruption events of stars by recoiling SMBHs. When a super-kick is imparted on a SMBH, there is a tightly bound cluster of stars recoiling with it. We show that these bound stars should be in an eccentric, apse-aligned disk where stars are strongly torqued to extremely high eccentricities. The corresponding rate of tidal disruption events in an eccentric disk is expected to be of order ~0.1 yr^-1 gal^-1, several orders of magnitude higher than in an isotropic cluster. We show that this high expected rate of tidal disruption events in an eccentric disk implies off-nuclear or extragalactic tidal disruption events as viable and likely observables of a recoiling or rogue SMBH.

Hyun: Understanding galaxy evolution is one of the big subjects in modern astronomy. Galaxy clusters and superclusters, which sit on the top of the hierarchy of structure formation in the universe, are valuable objects to witness various types of galaxies and environments and study how the properties of galaxies change with their surroundings. Submm galaxies are holding hints to reveal the mystery of star formation history in the early universe. In this talk, I will introduce two parts of my thesis. First, I will introduce the study of galaxy evolution in the galaxy clusters with the large-scale structure environment in the SA22 field. From this study, we checked the `web feeding model,’ which is that more linked (with their environment) galaxy clusters have less quenched population by investigating the correlation between properties of confirmed galaxy clusters and the large-scale structure environment. Second, I will present the newly found submm galaxies(SMGs) with JCMT SCUBA-2, star-forming populations having the key to revealing the hidden star formation in the universe, in the JWST Time Domain Field near the north ecliptic pole.