2003 Fiscal Year Final Research Report Summary
A Statistical Study of Massive Star-Cluster Formation
| Project/Area Number |
14540231
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | KUMAMOTO GAKUEN UNIVERSITY |
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Principal Investigator |
KUMAI Yasuki KUMAMOTO GAKUEN UNIVERSITY, Faculty of Commerce, Associate Professor, 商学部, 助教授 (30299664)
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| Project Period (FY) |
2002 – 2003
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| Keywords | galaxies / globular clusters / super star clusters / pulous star clusters / nuclear star clusters / structure parameters / galactic environment |
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| Research Abstract |
The main results of this study are the followings.
1.We found a common tight correlation between cluster mass and mean density inside half-light radius of the cluster among globular clusters, nuclear star clusters, and young massive star clusters in nearby galaxies, in spite of their large difference in their age and environment. However, there exists systematic difference in this correlation between inner and outer regions in a globular cluster system of nearby galaxies, as well as correlations among structure parameters of the clusters.
2.Among nearby elliptical and SO galaxies, the trend can be seen that their globular cluster system has a shallower slope in cluster number-density radial distribution and includes larger numbers of clusters relative to luminosity of their parent galaxy, as number density of galaxies around the host galaxy increases.
3.Nuclear star clusters (NSCs) are brighter in larger host galaxies, but there can be seen a sign that galactic bars control NSC formation mechanism.
4.We made a CO mapping observation of a peculiar galaxy NGC 2276, and found that the violent star forming region with which young massive star clusters appear to associate is probably activated by ram pressure of external gas around the galaxy.
5.Central dominant elliptical galaxies in galaxy clusters, which often have quite large specific frequency of globular clusters, show statistical evidence that their formation and evolution are seriously affected by both internal and external processes of the host cluster evolution : merger history of the host cluster and sink of surrounding member galaxies toward the cluster center through dynamical friction.
6.We found by X-ray data analyses that isolated over-luminous elliptical galaxies (IOLEGs) have similar dark halo with galaxy groups both in quantity and structure, but mass-to-light ratios of IOLEGs seriously contradict a widely believe scenario that they are "fossils" of galaxy groups.
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