• Title/Summary/Keyword: galactic center

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Spectroscopic Identification of Massive Young Stellar Objects in the Galactic Center

  • An, Deok-Keun
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.1
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    • pp.83.2-83.2
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    • 2011

  • I present results from the Spitzer/IRS study to identify massive young stellar objects (YSOs) in the Galactic Center (GC). Our sample of 107 YSO candidates was selected based on Spitzer/IRAC colors in the central 300 pc region of the Milky Way Galaxy. We obtained IRS spectra over $5{\mu}m$ to $35{\mu}m$, and identified massive YSOs by the presence of a $15.4{\mu}m$ shoulder on the absorption profile of $15{\mu}m$ $CO_2$ ice, suggestive of high $CH_3OH$ abundance on $CO_2$ ice grains. This $15.4{\mu}m$ shoulder is clearly observed in 16 sources and possibly observed in an additional 19 sources. We further show that 9 massive YSOs reveal molecular gas-phase absorption from $CO_2$, $C_2H_2$, and/or HCN, which traces warm and dense gas in YSOs. Our results provide the first spectroscopic census of the massive YSO population in the GC.

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Environmental Dependence of High-redshift Galaxies in CFHTLS W2 Field

  • Paek, Insu;Im, Myungshin;Kim, Jae-Woo
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.36.1-36.1
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    • 2018

  • Star formation activity of galaxies, along with color and morphology, show significant environmental dependence in local universe, where galaxies in dense environment tend to be more quiescent and redder. However, many studies show that such environmental dependence does not continue at higher redshifts beyond z~1. The question of how the environmental dependence of galactic properties have developed over time is crucial to understanding cosmic galactic evolution. By combining data from Canada-France-Hawaii Telescope Legacy Survey(CFHTLS), Infrared Medium-Deep Survey(IMS), and other surveys, the photometric redshifts of galaxies in CFHTLS W2 field were estimated by fitting spectral energy distribution. The distribution of galaxies was mapped in redshift bins of 0.05 interval from 0.6 to 1.4. For each redshift bin, the number density was mapped. The galaxies in high density regions were grouped into clusters using friend-of-friend method. The color of galaxies were analyzed to study the correlation with redshift as well as environmental difference between field galaxies and cluster member galaxies.

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