At present, I am particularly interested in the following two subjects in extra galactic astronomy. I tackle these problems primarily using Subaru and ALMA telescopes.
(1) Formation and evolution of porto-clusters of galaxies:
Galaxies often exist as groups or clusters. How are those systems formed in the Universe and how are the galaxies therein formed and evolve under the effects of surrounding environments? We search for progenitors of galaxy clusters further and further away from us in order to watch their formation in action in the early Universe. It is also known that present-day clusters are dominated by quiescent elliptical type galaxies, and we also investigate the origin of such cosmic habitat segregation.
(2) Formation of massive galaxies in the early Universe:
In the early Universe, it is predicted that small mass galaxies were formed first and they subsequently
merge together and grew to larger systems with time. This means that if we find massive galaxies in the early Universe when the cosmic age is still young, we can put strong constraints on the theory of galaxy formation. Galaxy formation must have started at very early epoch in the Universe and have proceeded in an accelerated manner. We have developed our unique filters on near-infrared instruments to search for the most distant massive galaxies. We expect to find such objects in proto-clusters, as the galaxy formation is expected to be accelerated in high density environments.