• Title, Summary, Keyword: stars: formation

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Intracluster Light Study of the Distant Galaxy Cluster SPT2106-5844 at z=1.132 with Hubble Space Telescope Infrared Imaging Data

  • Joo, Hyungjin;Jee, Myungkook James;Ko, Jongwan
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.2
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    • pp.76.3-76.3
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    • 2019
  • Intracluster stars are believed to be gravitationally bound to a galaxy cluster, however, not to individual cluster galaxies. Their presence is observed as diffuse light typically in the central region extended from the brightest cluster galaxy. The diffuse light, often referred to as intracluster light (ICL), is difficult to quantify in distant high-redshift galaxy clusters because of the significant surface brightness dimming although ICL observations in high-redshift clusters provide powerful constraints on the origin of intracluster stars. In this poster, we present ICL study of the distant galaxy cluster SPT2106-5844 at z=1.132 with Hubble Space Telescope IR imaging data. With careful control of systematics, we successfully quantify the total amount of the ICL, measure the color profile, and obtain its two-dimensional distribution. Our measurement of the high abundance of the intracluster stars in this young cluster favors the ICL formation scenario, wherein production of intracluster stars are predominantly associated with the BCG formation.

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TRAO Survey of Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO FUNS). III. Dynamics of filaments in different star forming environments

  • Chung, Eun Jung;Kim, Shinyoung;Yoo, Hyunju;Lee, Chang Won
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.69.2-69.2
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    • 2019
  • Recent high resolution IR observations reveal that molecular clouds are filamentary and such a structure is ubiquitous over various star-forming environments, and it is clear that filaments play a crucial role in the formation of cores and stars. However, the formation process of dense cores in the filaments are still unknown. To investigate this issue in detail, we have carried out TRAO FUNS (TRAO survey of nearby Filamentary molecular clouds, the Universal Nursery of Stars) toward various star forming filamentary molecular clouds. In this presentation, we will report the first look results of filaments and dense cores in MCLD 123.5+24.9 and IC 5146, which are known as a quiescent, non-star-forming region and an active, high-mass star forming region, respectively. By comparing the kinematic properties of filaments and dense cores in different star forming environments, we verified the formation scenario of filaments and dense core, i.e., gravoturbulent fragmentation via supersonic motions.

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A disk around a massive young stellar object (MYSO) revealed by the high resolution NIR spectroscopy

  • Kang, In;Lee, Jeong-Eun;NehaSharma, NehaSharma;Park, Sun kyung;Yoon, Sung-Yong
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.67.3-67.3
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    • 2019
  • Massive stars play an important role in terms of their feedback, but their formation process is poorly understood. Direct observational evidence for the formation of massive stars through accretion disks is rare. Hence the detection of disks in massive young stellar objects (MYSOs), if any, could be important to constrain the formation process of massive stars. The inner gaseous disk can be observed by the high-resolution near-infrared spectroscopy. We observed a MYSO, Min 2-62, using IGRINS and detected a double peak feature, which could be an evidence of a rotating disk, in the Bracket and Pfund series lines. We report the preliminary observational results of Min 2-62 with IGRINS.

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Detecting the Signature of the First Stars through Planck CMB Polarization Observation

  • Ahn, Kyungjin
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.76.2-76.2
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    • 2012
  • We present the first simulations of cosmic reionization that include the first stars and their radiative feedback that limited their formation, in a volume large enough to capture the spatial variations that affected the process and its observability. We show hat these first stars made reionization begin much earlier than without, and was reatly extended, which boosts the intergalactic electron-scattering optical depth and the large-angle polarization fluctuations of the cosmic microwave background (CMB) significantly. Although within current WMAP uncertainties, this will enable Planck see he signature of the first stars at high redshift, currently undetectable by other probes.

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Secular Evolution of Nuclear Bulges through Sustained Star Formation

  • Kim, Sung-Soo S.;Saitoh, Takayuki;Jeon, Myoung-Won;Merritt, David;Figer, Donal F.;Wada, Keiich
    • The Bulletin of The Korean Astronomical Society
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    • v.35 no.1
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    • pp.72.1-72.1
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    • 2010
  • Gas materials in the inner Galactic disk continuously migrate toward the Galactic center (GC) due to interactions with the bar potential, magnetic fields, stars, and other gaseous materials. In case of the Milky Way, those in forms of molecules appear to accumulate around 200 pc from the center (the central molecular zone, CMZ) to form stars there and further inside. The bar potential in the GC is thought to be responsible for such acculmulation of molecules and subsequent star formation, which is believed to have been continous throughout the lifetime of the Galaxy. We present 3-D hydrodynamic simulations of the CMZ that consider self-gravity, radiative cooling, and supernova feedback, and discuss the efficiency and role of the star formation in that region. We find that the gas accumulated in the CMZ by a bar potential of the inner bulge effectively turns into stars, supporting the idea that the stellar cusp inside the central 200 pc is a result of the sustained star formation in the CMZ. The obtained star formation rate in the CMZ, 0.03-0.1 Msun, is consistent with the recent estimate based on the mid-infrared observations by Yusef-Zadeh et al. We discuss the secular evolution of nuclear bulges in general, based on our results.

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A SURVEY OF T TAURI STARS WITH AKARI

  • Takita, S.;Kataza, H.;Kitamura, Y.;Ueno, M.;Oyabu, S.;Ishihara, D.;Ita, Y.
    • Publications of The Korean Astronomical Society
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    • v.27 no.4
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    • pp.185-186
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    • 2012
  • We have carried out a survey of T Tauri stars (TTSs) in a 1,800-square-degrees region toward the Taurus-Auriga star forming region with the AKARI Mid-Infrared All-Sky Survey. By combination of AKARI, 2MASS, and UCAC surveys, we created new criteria to chose TTS candidates. We also considered Asymptotic Giant Branch stars and galaxies, which have similar infrared colors, to separate TTSs from these sources. On the basis of our criteria, we find 27 new TTS candidates. To verify our criteria, we performed follow-up observations for them and confirmed that 23 are TTSs.

DUST GRAINS IN AGB STARS AS SOURCES OF INTERSTELLAR DUST

  • SUH KYUNG- WON
    • Journal of The Korean Astronomical Society
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    • v.37 no.4
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    • pp.289-294
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    • 2004
  • The main sources of interstellar dust are believed to be dust envelopes around AGB stars. The outflowing envelopes around the long period pulsating variables are very suitable place for massive dust formation. Oxygen-rich silicate dust grains or carbon-rich dust grains form in the envelopes around AGB stars depending on the chemical composition of the stellar surface. The dust grains expelled from AGB stars get mixed up and go through some physical and chemical changes in interstellar medium. There are similarities and differences between interstellar dust and dust grains in AGB stars. The mass cycle in the Galaxy may be best manifested by the fact that the dust grains at various regions have many similarities and understandable differences.

The first detection of intracluster light beyond a redshift of 1

  • Ko, Jongwan;Jee, Myungkook J.
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.39.1-39.1
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    • 2019
  • Not all stars in the Universe are gravitationally bounded to galaxies. Since first discovered in 1951, observations have revealed that a significant fraction of stars fills the space between galaxies in local (low-redshift) galaxy clusters, observed as diffuse intracluster light (ICL). Theoretical models provide mechanisms for the production of intracluster stars as tidally stripped material or debris generated through numerous galaxy interactions during the hierarchical growth of the galaxy cluster. These mechanisms predict that most intracluster stars in local galaxy clusters are long-accumulated material since z~1. However, there is no observational evidence to verify this prediction. Here we report observations of abundant ICL for a massive (above $10^{14}$ solar masses) galaxy cluster at a redshift of z=1.24, when the Universe was 5 billion years old. We found that more than 10 per cent of the total light of the cluster is contributed by the diffuse ICL out to 110 kpc from the center of the cluster, comparable to 5-20 per cent in local, massive galaxy cluster. Furthermore, we found that the colour of the brightest cluster galaxy located in the core of the cluster is consistent with that of the ICL out to 200 kpc. Our results demonstrate that the majority of the intracluster stars present in the local Universe, contrary to most previous theoretical and observational studies, were built up during a short period and early (z>1) in the history of the Virgo-like massive galaxy cluster formation, and might be concurrent with the formation of the brightest cluster galaxy.

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