GPPU Seminar

Date

15:00-17:00, November 29th, 2024

Place

(hybrid) Room 745, Science Complex B (H-03), Zoom registration map

Abstract

1) The formation and evolution of galaxies and their supermassive black holes are tightly related to the surrounding environment. Since the star formation activities in the Universe are thought to have peaked at ~10 Gyrs ago, it is the critical epoch for us to witness the cosmic structure growth and galaxy evolution in action. In this seminar, I will introduce physical information that can be derived from the observable properties of distant galaxies and their environmental dependencies. I will also report on a unique structure at the Universe of 11 Gyrs ago, hosting proto-clusters and their surrounding large-scale structure, which provides us with an ideal laboratory to investigate the role of the environment and supermassive black holes in galaxy formation and evolution.

2) The current benchmark model based on cold dark matter suggests that galaxies have grown through repeated mergers and accretions of smaller galaxies via gravitational interactions. The results from galaxy formation simulations show that the accretion history is imprinted in the stellar halo, the region surrounding a galactic disk. Our galaxy, the Milky Way, has long been the focus of understanding the structure of galaxies based on stars. Currently, the halo structure within 30 kpc from the Galactic center has been well studied using chemo-dynamical information of stars. However, the halo structure beyond 30 kpc has not yet been clarified. Due to its extremely long relaxation timescale of about 1 billion years, it provides valuable clues about the past orbits of accreted galaxies. In this study, we have revealed the halo structure within 100 kpc using photometry of abundant main sequence turn-off stars obtained with Hyper Suprime-Cam mounted on the Subaru Telescope. We have derived density profiles for different lines of sight and have found that the halo structure is anisotropic beyond 30 kpc. In this talk, I will carefully introduce the basic concepts of our study. Then, we will discuss the origin of the anisotropy with special attention to the past orbit of the Large Magellanic Cloud.

Point

GSP 1