2005 Fiscal Year Final Research Report Summary
A Comparative Study of Intracluster Stellar Populations
| Project/Area Number |
16540212
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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 | The University of Tokyo |
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Principal Investigator |
OKAMURA Sadanori The University of Tokyo, Graduate School of Science, Professor, 大学院・理学系研究科, 教授 (20114423)
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| Co-Investigator(Kenkyū-buntansha) |
YASUDA Naoki The University of Tokyo, Institute for Cosmic Ray Research, Associate Professor, 宇宙線研究所, 助教授 (80333277)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Planetary nebulae / Cluster of Galaxies / Intracluster space / Virgo cluster of galaxies / Coma cluster of galaxies |
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| Research Abstract |
There are stars in a cluster of galaxies that do not belong to any galaxy in the cluster. They are called the intracluster stellar population (ICSP). The aim of this research is to investigate the properties and the origin of the ICSP by a new method that utilizes intracluster planetary nebulae (ICPNe) as the probe of the ICPS. More specifically, we aimed to study first the spatial distribution, velocity structure, and metallicity of the ICPNe in the Virgo cluster of galaxies. Then we aimed to detect the ICPNe in the Coma cluster of galaxies which is in a different stage of dynamical evolution, and to investigate if there is any difference in the properties of the ICPNe in the two clusters.
We made spectroscopy of ICPNe in three fields in the central region of the Virgo cluster. It is found that the velocity distributions of the ICPNe are very different among the three fields. This implies that the Virgo cluster is still under construction phase and it is in a dynamically non-uniform and non-equilibrium state.
We observed the Coma cluster of galaxies which is seven times more distant than the Virgo cluster. Narrow band imaging technique we used for the Virgo cluster is no more useful and we devised a new technique called MSIS (Multi-Slit Imaging Spectroscopy). First observation led to a successful detection of 40 planetary nebulae. It is found that the velocity distribution of 35 ICPNe among the 40 shows a double-peak structure. This means that ICSP is not yet well-mixed even in the core of a dynamically evolved cluster such as the Coma cluster.
Our observation is the first to detect planetary nebulae in the Coma cluster and make the record of most distant stellar objects ever detected except for supernovae.
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