談話会
Colloquium

Ronaldo Laishram (Tohoku U.)
The 3D large scale structures of star forming galaxies and the projection corrected environmental effects back to z=1.5 revealed by the novel double narrow-band filter technique
Galaxies are distributed inhomogeneously on small scales in the Universe and thus define large-scale structures. Understanding the evolution of galaxies is to determine precisely how galaxies change their properties as a result of the hierarchical growth of large-scale structures. The difficulty is the need for accurate determination of the redshift to determine the precise environment of the galaxies. We present a very unique and novel method to estimate accurate redshifts of star-forming galaxies by measuring the flux ratio of the same emission line observed through two adjacent narrow-band filters. We apply this method to our NB921 and new NB926 data taken with Hyper Suprime-Cam on the Subaru Telescope. We obtain redshifts for [OII] emission line galaxies at z ∼ 1.5, [OIII] emission line galaxies at z~ 0.84 and [Ha] emission-line galaxies at z~0.41. This allows us to reveal 3D structures and can correct the projection effect. The projected celestial distribution does not precisely trace the real distribution of galaxies, indicating the importance of the three-dimensional view of structures to properly identify and quantify galaxy environments. We then investigate the projection corrected environmental dependence of galaxy properties.

Tomoaki Ishiyama (Chiba U.)
Supercomputer simulations of dark matter structure formation in the Universe
I report the results of large cosmological N-body simulations of small and large scale structure formation in the Universe. In the first topic, I will show the density structures of subhalos of dwarf spheroidal galaxies and discuss how we can constrain the nature of dark matter by comparing with observations. In the second topic, I will introduce the Uchuu suite of large high-resolution cosmological N-body simulations. The largest simulation, named Uchuu, consists of 2.1 trillion dark matter particles in a box of 2.0 Gpc/h. We can follow the evolution of dark matter halos (and subhalos) spanning from dwarf galaxies to massive galaxy cluster hosts. We make publicly available various N-body products, as part of Data Release 1. I will also present a roadmap for Data Release 2, in which galaxies and AGN mock catalogs constructed by various models are provided.