1999 Fiscal Year Final Research Report Summary
A Research on the Evolution of Population III Stars and on the Method of Their Search
| Project/Area Number |
09640308
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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 | HOKKAIDO UNIVERSITY |
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Principal Investigator |
FUJIMOTO Masayuki Hokkaido University, Grad. School of Sci., Professor, 大学院・理学研究科, 教授 (00111708)
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| Co-Investigator(Kenkyū-buntansha) |
JUGAKU Jun Tokai University, Research Inst. Of Cicilization, Pro., 文明研究所, 教授 (50012795)
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| Project Period (FY) |
1997 – 1999
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| Keywords | stellar evolution / metal-deficient stars / early Universe / Galaxy formation / carbon stars / nucleosynthesis |
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| Research Abstract |
The purpose of this research is to discuss theoretically and observationally the possibility of searching for Population III stars, which have been born first in our Universe and are yet to be discovered. These stars have been composed of the primordial matter processed by the Big-Bang nucleosynthesis, and hence, totally devoid of carbon and heavier metal elements. It is only low-mass stars not heavier than 0.8 solar masses that survive to date as nuclear burning stars.
It has been known that such low-mass, population III stars become carbon stars with enhanced nitrogen. We have extended the exsistent computation in the parameter region of initial mass and metallicity to present a general picture concerning the evolution to carbon stars: The formation mechanism of carbon stars with extremely low metallicity is different from those of metal-richer correspondences, which gives a result consistent with the observation that a fraction of carbon stars increases greatly for low-metalliclty of [Fe/H]<-2.5.
On the basis of these theoretical results, we propose a new method of search for population III stars to detect nitrogen-rich carbon stars by aid of molecular lines of carbon and nitrogen and further to discriminate them with the nitrogen/carbon ratio.
In order to check the validity of this new method, we made test observations by using Schmidt telescope with 2KCCD at Kiso observatory, the Uniersity of Tokyo.
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