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Research Fields

Welcome to OU-TAP group. In our research, emphasis is placed on clarification of fundamental physical processes and universal laws that determine the origin, structure and evolution of the universe and astronomical bodies.

Listed below are the on-going research subjects in our group.

Clusters of galaxies, and active galactic nuclei

Clusters of galaxies are filled with hot X-ray gas (intracluster medium). X-ray observations have shown that there should be unknown heating sources in their central regions. We are trying to find out what the sources are. Active galactic nuclei (AGNs) are the most promising candidate, and we study the energy input in the form of jets launched by the AGNs. Clusters have a lot of high energy particles (cosmic-rays). We are also studying the acceleration mechanisms of these particles. We approach these problems in both theoretical and observational ways.

Large-scale structure formation and evolution of galaxies

Nonlinear evolution of cosmological density perturbations and the large-scale structure formation; Evolution of clusters of galaxies, and the relation between the cluster parameters and the cosmological parameters; Construction of a realistic galaxy formation scenario based on high redshift observational data; Environmental and morphological dependencies in evolution of galaxies.

Active galactic nuclei and high energy astrophysics

Effects of electron-positron pairs in high temperature accretion disks; Vertical structure and radiation spectrum of the standard accretion disk model; Gamma-ray radiation from relativistic jets; Acceleration of relativistic jets by radiation; Statistical acceleration of cosmic rays by shock waves. Other high energy astrophysical phenomena including pulsars, X-ray binaries and gamma-ray bursts.

The origin of cosmic-rays (CRs)

The origin of cosmic-rays (CRs) is not clear. Although supernova remnants (SNRs) are known to be accelerators of CRs at TeV. We are interested in theorigin of CRs at >TeV, and explore various options such as SagittariusA*, which is an active galactic nucleus at the center of the Milky-Way.