Researcher Information

Kazuo Sorai

Associate Professor

Observational astronomy of galaxy evolution

Department of Physics, Nonlinear Physics


Observational studies of galaxy evolution from points of view of interstellar gas and star formation. Joining the project of the Antarctic Terahertz Telescops.

Fieldgalactic astronomy
Keywordgalaxy, interstellar gas, star formation, galaxy evolution, radio astronomy, Antarctic astronomy

Introduction of Research

I have investigated to make clear how galaxies have evolved from a viewpoint of interstellar gas and star formation mainly through observations with radio telescopes. Galaxies are assemblies of stars and interstellar medium, and the Milky Way is one of examples. The shape of galaxies is various, for example, there are spiral galaxies such as the Milky Way or the neighboring Andromeda galaxy, while there are galaxies whose shape is elliptical or irregular. Properties of galaxies located in dense regions are different from those of isolated galaxies. It is important to make clear how such variety results from, in order to understand galaxy formation and evolution. I have observationally investigated distributions, dynamics, physical properties of interstellar gas, which is material of stars, and relation among them and star formation activity in nearby galaxies. In recent years, I have engaged in a project that imaged many nearby galaxies in molecular gas tracer with the Nobeyama 45-m radio telescope, “CO multi-line imaging of nearby galaxies” (COMING). (see image “CO images of 147 nearby galaxies taken in COMING project”)
I have also an interest in development of telescopes and observational instruments. I developed the wide bandwidth radio spectrometers settled on the 45-m telescope. I engaged in improvement and operation of the Tomakomai 11-m radio telescope, and developed an automatic remote operation system of the telescope. (see photo “Tomakomai 11-m radio telescope”) In recent years, I have joined a project to construct terahertz telescopes in the Antarctica.

CO images of 147 nearby galaxies taken in COMING project. White pseudo color represents that molecular gas is rich.
Tomakomai 11-m radio telescope. It worked as a single-dish and a component of very long baseline interferometer (VLBI) in frequency bandwidth of 21.3 - 24.3 GHz, but now its operation was finished.

Representative Achievements

CO Multi-line Imaging of Nearby Galaxies (COMING) IV. Overview of the Project, Sorai, K., Kuno, N., Muraoka, K., Miyamoto, Y., Kaneko, H., Nakanishi, H., Nakai, N., Yanagitani, K., Tanaka, T., Sato, Y., Salak, D., Umei, M., Morokuma-Matsui, K., Matsumoto, N., Ueno, S., Pan, H.-A., Noma, Y., Takeuchi, T.T., Yoda, M., Kuroda, M., Yasuda, A., Yajima, Y., Oi, N., Shibata, S., Seta, M., Watanabe, Y., Kita, S., Komatsuzaki, R., Kajikawa, A., Yashima, Y., Cooray, S., Baji, H., Segawa, Y., Tashiro, T., Takeda, M., Kishida, N., Hatakeyama, T., Tomiyasu, Y. Saita, C., Publications of the Astronomical Society of Japan, 2019, accepted
Properties of Molecular Gas in the Bar of Maffei 2, Sorai, K., Kuno, N., Nishiyama, K., Watanabe, Y., Matsui, H., Habe, A., Hirota, A., Ishihara, Y., Nakai, N., Publications of the Astronomical Society of Japan, 2012, Vol.64, No.3, pp.51:1-10
Large-scale NH3 Observations toward the Galactic Star Forming Regions I. W 51 Molecular Clouds Complex, Sorai, K., Habe, A., Nishitani, H., Hosaka, K., Watanabe, Y., Miwa, S., Ohishi, Y., Motogi, K., Minamidani, T., Awano, J., Sumida, S., Fukuya, Y., Uchida, R., Kaneko, N., Fujimoto, M. Y., Koyama, Y., Kimura, M., Nakai, N., Publications of the Astronomical Society of Japan, 2008, Vol.60, No.6, pp.1285–1296
Distribution and Kinematics of Molecular Gas in Barred Spiral Galaxies. II. NGC 253, Sorai, K., Nakai, N., Kuno, N., Nishiyama, K., Hasegawa, T., Publications of the Astronomical Society of Japan, 2000, Vol.52, pp.785–802
Digital spectrometers for the Nobeyama 45-m telescope, Sorai, K., Sunada, K., Okumura, S. K., Tetsuro, I., Tanaka, A., Natori, K., Onuki, H., Proc. SPIE Vol.4015, pp.86–95, Radio Telescopes, Harvey R. Butcher; Ed., 2000
Academic degreePh.D.
Self Introduction

I come from Osaka.

Academic backgroundBachelor of Science, Kyoto University, 1993
Master of Science in Astronomy, The University of Tokyo, 1995
Ph.D. in Astronomy, The University of Tokyo, 1998
2012-Present Associate Professor, Hokkaido University
2017-Present Associate Professor, University of Tsukuba (cross-appointment)
Affiliated academic societyThe Astronomial Society of Japan, International Astronomical Union
ProjectNRO 45-m Telescope Legacy Program, "CO Multi-line Imaging of Nearby Galaxies" (COMING)
Room addressGeneral Research Building 2 2-316