SCYON Abstract

Received on October 20 2008

Clustering of Emission-line Stars in the W5E HII Region

AuthorsM. Nakano (1), K. Sugitani (2), T. Niwa (3), Y. Itoh (3), and M. Watanabe (4)
Affiliation(1) Faculty of Education and Welfare Science, Oita University, Oita 870-1192, Japan
(2) Graduate School of Natural Sciences, Nagoya City University, Mizuho-ku, Nagoya 467-8501, Japan
(3) Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan
(4) Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720, USA
Accepted byPubl. Astron. Soc. Japan
Contactmnakano@cc.oita-u.ac.jp
URLhttp://pasj.asj.or.jp/v60/n4/600410/600410.pdf
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Abstract

We have made a new survey of emission-line stars in the W5E HII region to investigate the population of PMS stars near the OB stars by using the Wide Field Grism Spectrograph 2 (WFGS2). A total of 139 Hα emission stars were detected and their g'i'-photometry was performed. Their spatial distribution shows three aggregates, i.e., two aggregates near the bright-rimmed clouds at the edge of the W5E HII region (BRC 13 and BRC 14) and one near the exciting O7V star. The age and mass of each Hα star were estimated from an extinction-corrected color-magnitude diagram and theoretical evolutionary tracks. We found, for the first time in this region, that the young stars near the exciting star are systematically older (4 Myr) than those near the edge of the HII region (1 Myr). This result supports that the formation of stars proceeds sequentially from the center of HII region to the eastern bright rim. We further suggest a possibility that the birth of low-mass stars near the exciting star of the HII region precedes the production of massive OB stars in the pre-existing molecular cloud.