1993 Fiscal Year Final Research Report Summary
Formation of Globular Clusters in Galaxies
| Project/Area Number |
04452013
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Astronomy
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| Research Institution | Nagoya University |
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Principal Investigator |
FUJIMOTO Mitsuaki Nagoya University Department of Physics Professor, 理学部, 教授 (70022580)
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| Co-Investigator(Kenkyū-buntansha) |
SAWA Takefumi Nagoya University Department of Physics and Astronomy Associate Professor, 教育学部, 助教授 (90111864)
HANAWA Tomoyuki Nagoya University Department of Physics Research Associate, 理学部, 助手 (50172953)
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| Project Period (FY) |
1992 – 1993
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| Keywords | globular clusters / galaxies / gravitational instability / binary clusters / 回転 / 星団形成 |
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| Research Abstract |
We made a model for the orbits of the Large and Small Magellanic Clouds (LMC and SMC) to reproduce the density and velocity destribution of hydrogen gas in the Magellanic stream. In the successful model LMC and SMC from a gravitationally bound pair and have revolved around the Galaxy over the past - 10^<10> y. They exprienced a close encounter every - 10^9 y and have been agitated by tidal force repeatedly to keep the interstellar gas turbulent with the turbulent velocity higher than (〕SY.gtoreq.〔) 50 km s^<-1>.
Turbulent eddies (gas clouds) collide with each other frequently and form compressed gas layers at the interfaces. The compressed gas layrs rotate and have internal velocity shear because the collisions are usually off-center and rarely head-on. Our linear stability analysis showed that the compressed gas layrs fragment into gravitationally bound clumps with the mass of 10^4 - 10^6 M_<(〕SY.sun.〔)> after it grows in mass and its self-gravity becomes appreciable. The gaseous clumps cool rapidly due to their high density and cascade into much smaller fragments, finally froming gravitationally-bound stellar systems or globular clusters.
We thus conclude that globular clusters are not cosmological objects formed only in the early universe but ordinary ones formed at any epoch in the galaxies in which a large amount of interstellar gas has an unorganized motion with the velocity higher than 50 km s^<-1>. The color, age, and mass distributions of globular clusters manifest the history of the dynamical events experienced by the host galaxy.
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