LOW-METALLICITY YOUNG CLUSTERS IN THE OUTER GALAXY. I. Sh 2-207

ABSTRACT To study star formation in low-metallicity environments ([M/H] ∼ −1 dex), we obtained deep near-infrared (NIR) images of Sh 2-207 (S207), which is an H ii region in the outer Galaxy with a spectroscopically determined metallicity of [O/H] −0.8 dex. We identified a young cluster in the weste...

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Bibliographic Details
Published in:The Astronomical journal 2016-03, Vol.151 (3), p.50
Main Authors: Yasui, Chikako, Kobayashi, Naoto, Tokunaga, Alan T., Saito, Masao, Izumi, Natsuko
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Clusters
COMPARATIVE EVALUATIONS
Fittings
GALAXIES
Galaxy: abundances
infrared: stars
LUMINOSITY
MASS
METALLICITY
NEAR INFRARED RADIATION
open clusters and associations: general
protoplanetary disks
PROTOPLANETS
STAR CLUSTERS
STAR EVOLUTION
Star formation
STARS
stars: formation
stars: pre-main sequence
Stellar age
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Summary:ABSTRACT To study star formation in low-metallicity environments ([M/H] ∼ −1 dex), we obtained deep near-infrared (NIR) images of Sh 2-207 (S207), which is an H ii region in the outer Galaxy with a spectroscopically determined metallicity of [O/H] −0.8 dex. We identified a young cluster in the western region of S207 with a limiting magnitude of KS = 19.0 mag (10 ) that corresponds to a mass detection limit of 0.1 M and enables the comparison of star-forming properties under low metallicity with those of the solar neighborhood. From the fitting of the K-band luminosity function (KLF), the age and distance of the S207 cluster are estimated at 2-3 Myr and ∼4 kpc, respectively. The estimated age is consistent with the suggestion of small extinctions of stars in the cluster (AV ∼ 3 mag) and the non-detection of molecular clouds. The reasonably good fit between the observed KLF and the model KLF suggests that the underlying initial mass function (IMF) of the cluster down to the detection limit is not significantly different from the typical IMFs in the solar metallicity. From the fraction of stars with NIR excesses, a low disk fraction (
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/0004-6256/151/3/50