Structure Formation

There are rich structures in the present-day universe, such as stars, galaxies, and large-scale structure. We study how these objects are formed using large computer simulations and sophisticated theoretical models.

The standard Big Bang model posits that the universe was nearly homogeneous and very hot when it was born. Tiny "ripples" in the distribution of matter are generated through a rapid expansion phase called in ation in the very early universe. These primeval density  uctuations grow by the action of gravity, eventually forming luminous objects such galaxies.

The energy content of the universe and basic statistic that describe the condition of the early universe have been determined with great accuracy from recent observations of cosmic microwave background radiation, large-scale galaxy distribution and distant supernovae. Cosmology is now at a stage where theory can make solid predictions, whereas a broad class of observations can be directly used to verify them.

Our primary interests are in primordial star formation in the early universe, the formation and evolution of galaxies, and the formation of large-scale structure. Results from these studies will be used for making good plans and proposals for next generation large observational programs such as Subaru-HSC dark energy survey.

Group Members

Issha Kayo

Extraction of cosmological information from the large-scale structure of the Universe, particularly using the actual data taken by the Sloan Digital Sky Survey and virtual data generated by N-body simulations. Construction of a homogeneous catalog of gravitationally lensed quasars to constraint the dark energy.

Tsz Yan Lam

Distributions of dark matter halos and dark matter field. Environmental dependence of halo formation.

 Yen-Ting Lin

Atacama Cosmology Telescope (ACT) project, a large cluster survey that detects clusters via the Sunyaev-Zel'dovich eect (SZE). Analyses of the data from ACT, SDSS, and Subaru, to study the evolution of galaxies within clusters, as well as to use the statistical properties of clusters (such as clustering and abundance) to constrain cosmology.

Ikkoh Shimizu

Theoretical models of high redshift galaxies.

Naoshi Sugiyama

Investigation of linear evolution of structure in the universe and eect of magnetic elds.

Masahiro Takada

Observational and theoretical studies of gravitational lensing caused by hierarchical structures of the universe. Nature of dark side of the universe, dark matter and dark energy, with the gravitational lensing observables. Future Subaru Weak Lensing Survey.

Atsushi Taruya

Modeling dynamics and statistics of large-scale structure of
the Universe, and testing various cosmological scenarios and/or hypothesis through direct comparison between theory and observations. A pursuit of the prospects for future observations such as HSC and BOSS to constrain dark energy, massive neutrinos, primordial non-Gaussianity as well as to test theory of gravity.

Rajat Mani Thomas

21cm observations of the epoch of reionization. Fast computation of HII bubble growth in the early universe.

Marcos Valdes

Cosmic reionization and the nature of dark matter. High-energy astrophysics.

Naoki Yoshida

Formation of stars, galaxies and the large-scale structure of the universe using supercomputer simulations.