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Low-metallicity Young Clusters in the Outer Galaxy. III. Sh 2-127

Yasui, Chikako and Kobayashi, Naoto and Saito, Masao and Izumi, Natsuko and Skidmore, Warren (2021) Low-metallicity Young Clusters in the Outer Galaxy. III. Sh 2-127. Astronomical Journal, 161 (3). Art. No. 139. ISSN 0004-6256.

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In deep near-infrared imaging of the low-metallicity ([O/H] = −0.7 dex) H II region Sh 2-127 (S127) with Subaru/MOIRCS, we detected two young clusters with 413 members (S127A) in a slightly extended H II region and another with 338 members (S127B) in a compact H II region. The limiting magnitude was K = 21.3 mag (10σ), corresponding to a mass detection limit of ~0.2 M⊙. These clusters are an order of magnitude larger than previously studied young low-metallicity clusters and larger than the majority of solar neighborhood young clusters. Fits to the K-band luminosity functions indicate very young cluster ages of 0.5 Myr for S127A and 0.1–0.5 Myr for S127B, consistent with the large extinction (up to A_V ≃ 20 mag) from thick molecular clouds and the presence of a compact H II region and class I source candidates, and suggest that the initial mass function (IMF) of the low-metallicity clusters is indistinguishable from typical solar neighborhood IMFs. Disk fractions of 28% ± 3% for S127A and 40% ± 4% for S127B are significantly lower than those of similarly aged solar neighborhood clusters (~50%–60%). The disk fraction for S127B is higher than those of previously studied low-metallicity clusters (<30%), probably due to S127B's age. This suggests that a large fraction of very young stars in low-metallicity environments have disks, but the disks are lost on a very short timescale. These results are consistent with our previous studies of low-metallicity star-forming regions, suggesting that a solar neighborhood IMF and low disk fraction are typical characteristics for low-metallicity regions, regardless of cluster scales.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Saito, Masao0000-0003-0769-8627
Izumi, Natsuko0000-0003-1604-9127
Additional Information:© 2021. The American Astronomical Society. Received 2020 October 10; revised 2020 December 9; accepted 2020 December 10; published 2021 February 23. This work was supported by JSPS KAKENHI grant No. 26800094. We thank the Subaru support staff, in particular MOIRCS support astronomer Ichi Tanaka. We also thank Chihiro Tokoku for helpful discussions on the observation.
Group:Thirty Meter Telescope
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)26800094
Subject Keywords:Galaxy abundances; Infrared sources; Open star clusters; Metallicity; Protoplanetary disks; Star formation; Pre-main sequence; H II regions
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Galaxy abundances (574); Infrared sources (793); Open star clusters (1160); Metallicity (1031); Protoplanetary disks (1300); Star formation (1569); Pre-main sequence (1289); H II regions (694)
Record Number:CaltechAUTHORS:20210318-112750191
Persistent URL:
Official Citation:Chikako Yasui et al 2021 AJ 161 139
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108483
Deposited By: Tony Diaz
Deposited On:24 Mar 2021 21:41
Last Modified:24 Mar 2021 21:41

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