2002 Fiscal Year Final Research Report Summary
Survey of Intracluster Planetary Nebulae in the Virgo Cluster
| Project/Area Number |
13640231
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Astronomy
|
|---|
| Research Institution | The University of Tokyo |
|---|
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)
|
|---|
| Project Period (FY) |
2001 – 2002
|
| Keywords | Cluster of Galaxies / Stars in intracluster space / Planetary nebulae |
|---|
| Research Abstract |
In spring, 2001, we observed with Subaru telescope the area for one field of view of Suprime-cam, which is located in the core region of the Virgo cluster. We took broad-band V (15 min. exp.) and R (12 min. exp.) images in addition to narrow-band O[III]λ5007Å and Hαλ6563Å images. The results obtained in the present study are summarized in the following.
This was the first study to use the two emmission lines for the search of planetary nebulae. We defined the appropriate selection criteria for intracluster planetary nebulae (ICPNe) candidates based on the (O[III]-Hα) versus (O[III]-(V+R)) two-color diagram.
Using the newly setablished criteria, we found 38 secure ICPNe candidates in the 27'× 24' field in the cluster core region. Projected sky distibution of the 38 candidates is highly non-uniform, indicating possible association with M86-M84 subcluster. The fraction of diffuse intracluster light with respect to the light from galaxies was estimated to be 〜10%, and the baryonic fraction of the total mass including dark matter was calculated to be 〜20% in the observed field.
During the course of this study, we serendipitously found a compact HII region, which is far away from NGC 4388 and almost isolated from any galaxay. It is a small HII region powered by only a few OB stars. This is the first discovery of a star forming site so far away from a galaxy. Similar objects, if found in future, would have a significant impact on the formation process of galaxies.
Another seredipitous discovery was the extremely extended emission line regions around NGC 4388 in the deep Hα image. It is the largest of its kind with the size of 35kpc.
|
