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Related papers: Low-metallicity Young Clusters in the Outer Galaxy…

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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 HII region in the outer Galaxy with spectroscopically determined metallicity of [O/H] ~=…

Solar and Stellar Astrophysics · Physics 2016-02-17 Chikako Yasui , Naoto Kobayashi , Alan T. Tokunaga , Masao Saito , Natsuko Izumi

We present deep near-infrared (NIR) imaging of Sh 2-209 (S209), a low-metallicity (${\rm [O/H]} = - 0.5$ dex) HII region in the Galaxy. From the NIR images, combined with astrometric data from Gaia EDR3, we estimate the distance to S209 to…

Astrophysics of Galaxies · Physics 2023-02-08 Chikako Yasui , Naoto Kobayashi , Masao Saito , Natsuko Izumi , Yuji Ikeda

In deep near-infrared imaging of the low-metallicity (${\rm [O/H]}=-0.7$ 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…

Astrophysics of Galaxies · Physics 2021-03-03 Chikako Yasui , Naoto Kobayashi , Masao Saito , Natsuko Izumi , Warren Skidmore

There is a lack of state-of-the-art information on very young open clusters, with implications for determining the structure of the Galaxy. Our main objective is to study the timing and location of the star formation processes which yielded…

Astrophysics of Galaxies · Physics 2015-05-14 Antonio J. Delgado , Anlaug A. Djupvik , Emilio J. Alfaro

This study presents sensitive MIR photometry obtained with the Spitzer/IRAC for a young cluster in Sh 2-208 (S208) located in one of the lowest-metallicity HII regions in the Galaxy, ${\rm [O/H]} = -0.8$ dex. Previous studies suggested that…

Astrophysics of Galaxies · Physics 2021-06-30 Chikako Yasui

To fully understand the star formation process, we are compelled to study it in a variety of environments. Of particular interest are how star formation and the resulting initial mass function (IMF) vary as a function of metallicity. We…

Astrophysics of Galaxies · Physics 2025-05-20 M. Andersen , A. Brizawasi , Y. Cheng , J. C. Tan , R. Fedriani , J. J. Armstrong , M. Robberto

Recent work suggested that the variation of the initial mass function (IMF) of stars depends on the physical conditions, notably, the metallicity and gas density. We investigated the properties of two clusters, namely the main cluster (MC)…

Astrophysics of Galaxies · Physics 2024-04-11 Marie Zinnkann , Henriette Wirth , Pavel Kroupa

This work aims to the study of the Sh 2-307 HII region and related stellar population. Near-infrared imaging and spectroscopic observations in the direction of Sh 2-307 were performed using OSIRIS at SOAR Telescope. From J-, H- and K-band…

Astrophysics of Galaxies · Physics 2015-05-13 Alexandre Roman-Lopes

Using our deep optical and near-infrared photometry along with multiwavelength archival data, we here present a detailed study of the Galactic H II region Sh 2-305, to understand the star/star-cluster formation. On the basis of excess…

We have been investigating the metallicity dependence of star and planet formation, particularly focusing on the outer Galaxy with a Galactocentric distance ($R_g$) of $\gtrsim$15 kpc, where the metallicity is determined to be as low as…

Astrophysics of Galaxies · Physics 2020-10-02 Chikako Yasui

We are conducting a deep near-infrared (NIR) imaging survey of young embedded clusters in the extreme outer Galaxy (hereafter EOG), at the Galactic radius (R_g) of more than 18 kpc. The EOG is an excellent laboratory to study the nature of…

Astrophysics · Physics 2008-01-03 Chikako Yasui , Naoto Kobayashi , Alan T. Tokunaga , Masao Saito , Chihiro Tokoku

We present multiwavelength investigation of morphology, physical-environment, stellar contents and star formation activity in the vicinity of star-forming region Sh 2-100. It is found that the Sh 2-100 region contains seven HII regions of…

Astrophysics of Galaxies · Physics 2015-05-18 M. R. Samal , A. K. Pandey , D. K. Ojha , S. K. Ghosh , V. K. Kulkarni , N. Kusakabe , M. Tamura , B. C. Bhatt , M. A. Thompson , R. Sagar

The evolution of HII regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution and star formation efficiency. In this…

Solar and Stellar Astrophysics · Physics 2017-02-22 Jessy Jose , Gregory J. Herczeg , Manash R. Samal , Qiliang Fang , Neelam Panwar

The supermassive black hole at the center of the Milky Way plays host to a massive, young cluster that may have formed in one of the most inhospitable environments in the Galaxy. We present new measurements of the global properties of this…

Solar and Stellar Astrophysics · Physics 2015-06-12 Jessica R. Lu , Tuan Do , Andrea M. Ghez , Mark R. Morris , Sylvana Yelda , Keith Matthews

Located at the galactic anticenter, Sh 2-284 is a HII region which harbors several young open clusters; Dolidze 25, a rare metal poor (Z~0.004) young cluster, is one of these. Given its association with Sh 2-284, it is reasonable to assume…

Solar and Stellar Astrophysics · Physics 2015-05-19 F. Cusano , V. Ripepi , J. M. Alcala , D. Gandolfi , M. Marconi , S. Degl'Innocenti , F. Palla , E. W. Guenther , S. Bernabei , E. Covino , C. Neiner , E. Puga , S. Hony

There is much observational evidence that active star formation is taking place in the HII regions Sh 2-255 -- 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical…

We present the substellar mass function of star-forming clusters ($\simeq$0.1 Myr old) in a low-metallicity environment ($\simeq$$-$0.7 dex). We performed deep JWST/NIRCam and MIRI imaging of two star-forming clusters in Digel Cloud 2, a…

Astrophysics of Galaxies · Physics 2024-08-29 Chikako Yasui , Natsuko Izumi , Masao Saito , Ryan M. Lau , Naoto Kobayashi , Michael E. Ressler

Context: The discovery of new massive star clusters and massive stellar populations in previously known clusters in our Galaxy by means of infrared studies has changed our view of the Milky Way from an inactive to an active star-forming…

Solar and Stellar Astrophysics · Physics 2012-03-21 S. Ramírez Alegría , A. Herrero , A. Marín-Franch , E. Puga , F. Najarro , J. A. Acosta Pulido , S. L. Hidalgo , S. Simón-Díaz

We present a multi-wavelength study of the Sh2-138, a Galactic compact H II region. The data comprise of optical and near-infrared (NIR) photometric and spectroscopic observations from the 2-m Himalayan Chandra Telescope, radio observations…

Solar and Stellar Astrophysics · Physics 2015-11-04 T. Baug , D. K. Ojha , L. K. Dewangan , J. P. Ninan , B. C. Bhatt , S. K. Ghosh , K. K. Mallick

[Abridged] Twenty-six high-luminosity IRAS sources believed to be collection of stars in the early phases of high-mass star formation have been observed in the NIR (J, H, K) to characterize the clustering properties of their young stellar…

Astrophysics of Galaxies · Physics 2015-05-13 Fabiana Faustini , Sergio Molinari , Leonardo Testi , Jan Brand
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