| Project/Area Number |
07640399
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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 |
素粒子・核・宇宙線
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NAKAMURA Takeshi Kyoto University, Yukawa Inst., Prof, 基礎物理学研究所, 教授 (80155837)
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| Co-Investigator(Kenkyū-buntansha) |
TIBE Takeshi Kyoto University, COE Reseacher, 基礎物理学研究所, 講師(COE研究員)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1996: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1995: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Micro Lensing / Dark Matter / Star Formation / マイクロ重力レンズ / 銀河 / 白色矮星 / かっ色矮星 |
|---|
| Research Abstract |
If the density distribution rho (gamma) of MACHOs is spherically symmetric with respect to the Galactic center, it is shown that the minimal total mass M^<MACHO>_ of the MACHOs is 1.7<of sun> 10^<10>M_<<of sun>>gamma^<LMC>_7 where gamma^<LMC>_7 is the optical depth (gamma^<LMC>) toward the Large Magellanic Cloud (LMC) in the unit of 2<of sun> 10^<-7>. If rho (gamma) is a decreasing function of gamma, it is proved that M^<MACHO>_ is 5.6<of sun> 10^<10>M_<<of sun>>gamma^<LMC>_7. Several spherical and axially symmetric halo models of the Galaxy with a few free parameters are also considered. It is found that M^<MACHO>_ ranges from 5.6<of sun> 10^<10>M_<<of sun>>gamma^<LMC>_7 to-3<of sun> 10^<11>M_<<of sun>>gamma^<LMC>_7. For general case, the minimal column density SIGMA^<MACHO>_ of MACHOs is obtained as SIGMA^<MACHO>_ =25M_<<of sun>>pc^<-2>gamma^<LMC>_7. If the clump of MACHOs exist only halfway between LMC and the sun, M^<MACHO>_ is 1.5<of sun> 10^9M_<<of sun>>. This shows that the total mass of MACHOs is smaller than 5<of sun> 10^<10>M_<<of sun>>, i.e.-10% of the mass of the halo inside LMC,either if the density distribution of MACHOs is unusual or gamma^<LMC><<2<of sun> 10^<-7>.
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