2001 Fiscal Year Final Research Report Summary
Space Pnysics Developed by High-Precise Astrometry
| Project/Area Number |
12640242
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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 | National Astronomical Observatory |
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Principal Investigator |
TSUJIMOTO Takuji National Astronomical Observatory Fundametal Astrometry and Celrstial Mechamics Division, Research Associate, 位置天文天体力学研究系, 助手 (10270456)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAJIMA Tadashi National Astronomical Observatory Optical and Infrard Astrometry Division,Research Associate, 光学赤外線天文学観測システム研究系, 助手 (20300709)
GOUDA Ru National Astronomical Observatory Fundametal Astrometry and Celrstial Mechamics Division,Professor, 位置天文天体力学研究系, 教授 (50202073)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Astrometry / Hipparcos / DIVA |
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| Research Abstract |
The Hipparcos satellite have brought us a new era for the distance determination using the trigonometric parallaxes π of stars. Before Hipparcos, the ground-based observations offered π only for stars within a few tens pc, - and we are already at the stage to obtain π for stars with their distances extending to -1-2 kpc. As a result, the Hipparcos catalog invloves many valuable stars, of which Cepheid variables and RR Lyrae stars which serve as primary distance indicators are included. It is well-known that Cepheids obey the period-luminosity (PL) relation. The zero-point for PL gives a distance modulus MLMC to the Large Magellanic Cloud (LMC), which is no doubt an important step for determining the distances to distant galaxies and thus for the Bubble constant (H0). In the same manner, the RR ALyraes which obey the metallicty-luminosity (ML) relation also provide ^LMC- In addition, they are indeed used to determine the distances to the Galactic globular clusters and hence their ages.
… More
Instead of the indirect calibrations of these zero-points so far, Hipparcos has enabled us to derive them directly from π of Galactic Cepheids and RR Lyraes for the first time. However, in fact, direct calibrations have confronted a serious problem which comes from the fact that almost all of π for these variables are measured with very large error including negative parallaxes. In such a case, the distance d for each variable cannot be calculated from d(pc) = I/π. We therefore need do deduce the physical quantities statistically from the ensemble of Hipparcos parallaxes. In this research, we investigate how rigorous two statistical methods are to calibrate Hipparcos parallaxes. All discussions will end in the settlement of JILMC given by Hipparcos variables. The precise determination of biases and variances involved in the final results by the statistical calibrations is certainly required for not only the further study using Hipparcos data but also the future work using the highly-precise astrometric data brought by the ongoing space satellite projects such as DIVA and FAME. Less
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