M. Nakano, K. Sugitani, M. Watanabe, N. Fukuda, D. Ishihara, M. Ueno
We have made an extensive survey of emission-line stars in the IC 1396 HII
region to investigate the low-mass population of pre-main sequence (PMS) stars.
A total of 639 H-alpha emission-line stars were detected in an area of 4.2
deg^2 and their i'-photometry was measured. Their spatial distribution exhibits
several aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the HII region (Rim B and SFO 37, 38, 39, 41), and near
HD 206267, which is the main exciting star of the HII region. Based on the
extinction estimated from the near-infrared (NIR) color-color diagram, we have
selected pre-main sequence star candidates associated with IC 1396. The age and
mass were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. Most of our PMS candidates have ages of <
3 Myr and masses of 0.2-0.6 Mo. Although it appears that only a few stars were
formed in the last 1 Myr in the east region of the exciting star, the age
difference among subregions in our surveyed area is not clear from the
statistical test. Our results may suggest that massive stars were born after
the continuous formation of low-mass stars for 10 Myr. The birth of the
exciting star could be the late stage of slow but contiguous star formation in
the natal molecular cloud. It may have triggered to form many low-mass stars at
the dense inhomogeneity in and around the HII region by a radiation-driven
implosion.
View original:
http://arxiv.org/abs/1201.2761
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