• Title, Summary, Keyword: Galaxy: structure

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CENSUS AND ANALYSIS OF GALACTIC MOLECULAR CLOUDS

  • HOJAEV, A.S.
    • Publications of The Korean Astronomical Society
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    • v.30 no.2
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    • pp.107-108
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    • 2015
  • In this project, all available databases of molecular and gas-dust clouds in the Galaxy were cross-identified by taking into account available properties, including position, angular dimensions, velocity, density, temperature and mass. An initial list of about 7000 entries was condensed into a cross-identified all-sky catalogue containing molecular and gas-dust clouds. Some relationships were studied between the main physical features of clouds. Finally, we prepared a complex observing program and address future work for filling in the gaps.

Star-formation Properties of High-redshift (z~1) Galaxy Clusters Connected to the Large-scale Structure

  • Lee, Seong-Kook;Im, Myungshin;Hyun, Minhee;Park, Bomi;Kim, Jae-woo;Kim, Dohyung;Kim, Yongjung
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.40.2-40.2
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    • 2017
  • At local, majority of galaxies in the dense environment, such as galaxy cluster, are red and quiescent with little star-formation (SF) activity. However, a different picture emerges as we go to high redshift: (1) there exist non-negligible fraction of galaxies still forming stars actively even in dense environment, and (2) there is a significant cluster-by-cluster variation in the SF properties, such as quiescent galaxy fraction. In this presentation, we show the results of our study about the variation of quiescent galaxy fraction among high-redshift (z~1) galaxy clusters, based on the multi-object spectroscopic (MOS) observation with IMACS on the Magellan telescope. Our main result is that galaxy clusters which are connected with significant large-scale structure (LSS), well beyond the cluster scale, are more active in their SF activity, i.e., the quiescent galaxy fraction for these clusters is lower compared to the clusters which are detached from LSS.

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Cosmological parameter constraints from galaxy-galaxy lensing with the Deep Lens Survey

  • Yoon, Mijin;Jee, Myungkook James
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.54.3-55
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    • 2017
  • The Deep Lens Survey (DLS), a precursor to the Large Synoptic Survey Telescope (LSST), is a 20 deg2 survey carried out with NOAO's Blanco and Mayalltelescopes. DLS is unique in its depth reaching down to ~27th mags in BVRz bands. This enables a broad redshift baseline and is optimal for investigating cosmological evolution of the large scale structure. Galaxy-galaxylensing is a powerful tool to estimate averaged matter distribution around lensgalaxies by measuring shape distortions of background galaxies. The signal from galaxy-galaxy lensing is sensitive not only to galaxy halo properties, but also to cosmological environment at large scales. In this study, we measure galaxy-galaxy lensing and galaxy clustering, which together put strong constraints on the cosmological parameters. We obtain significant galaxy-galaxy lensing signals out to ~20 Mpc while tightly controlling systematics. The B-mode signals are consistent with zero. Our lens-source flip test indicates that minimal systematic errors are present in DLS photometric redshifts. Shear calibration is performed using high-fidelity galaxy image simulations. We demonstrate that the overall shape of the galaxy-galaxy lensing signal is well described by the halo model comprised of central and non-central halo contributions. Finally, we present our preliminary constraints on the matter density and the normalization parameters.

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EMISSION LINE VELOCITY FIELD OF THE MAGELLANIC IRREGULAR GALAXY NGC 4449

  • SASAKI MINORU;OHTANI HIROSHI;SAITO MAMORU;OHTA KOUJI;YOSHIDA MICHITOSHI;SHIMIZU TASUHlRO;KOYANO HISASHI;KOSUGI GEORGE;AOKI KENTARO;SASAKI TOSHIYUKI
    • Journal of The Korean Astronomical Society
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    • v.29 no.spc1
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    • pp.85-86
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    • 1996
  • The imaging spectroscopic observations of the Magellanic irregular galaxy NGC 4449 were made to show the detailed kinematic structure of the galaxy. Many filamentary structures and Several bubble-like structures are recognized in a 3D data cube of H$\alpha$ emission line. Velocity field shows the kpc-scale mosaic structure and counter- rotation of ionized gas.

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Ram Pressure Stripping of an elliptical galaxy in Abell 2670

  • Sheen, Yun-Kyeong;Smith, Rory;Jaffe, Yara;Kim, Minjin;Yi, Sukyoung
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.2
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    • pp.34.3-35
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    • 2016
  • Ram pressure stripping of early-type galaxies has been largely neglected until now because of their gas poor nature. MUSE IFU observation vividly reveal the presence of star-forming blobs and ionised gas tails, around an early-type galaxy in Abell 2670. The galaxy was identified as a post-merger galaxy with disturbed faint features, in MOSAIC 2 deep optical images. The imaging also revealed a series of star-forming blobs, situated in the direction facing away from the cluster centre. Thanks to the revolutionary wide field-of-view of the MUSE, combined with 8.2-m VLT (UT-4) at Cerro Paranal, we could simultaneously obtain IFU spectra of the blobs, as well as the galaxy. The MUSE spectra clearly confirms that the star-forming blobs are associated with the early-type galaxy. Moreover, MUSE reveals long ionised-gas tails, emanating from the galaxy. The quantity of gas indicates a gas rich progenitor has merged with the early-type galaxy. However the direction of the tails and blobs, and the blob morphology, appears to indicate that strong ram-pressure stripping may have stripped out gas brought in by the merger. We will present kinematic structure of the whole system (the galaxy, star-forming blobs, and gas tails), as well as the star formation history of the system, supporting a scenario where a recent galaxy merger is subjected to cluster environmental mechanisms.

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Identifying Cluster Candidates 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.1
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    • pp.59.2-59.2
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    • 2018
  • Recent studies of galaxy clusters have shown that the galaxy clusters in dense environment tend to have lower star formation rate in local universe with z < 1. However, this correlation is not significant in galaxy clusters with z > 1. The study of galaxy clusters around z=1 can yield insight into cosmological galaxy evolution. Nevertheless, the identification of galaxy clusters beyond the scope of immediate local universe requires wide field data in optical and near-infrared bands. By incorporating data from Canada-France-Hawaii Telescope Legacy Survey(CFHTLS) and Infrared Medium-Deep Survey(IMS), the photometric redshifts of galaxies in CFHTLS W2 field were calculated. Using spatial distribution and photometric redshifts, the galaxies in the field were divided into redshift bins. The image of each redshift bin was analyzed by measuring the number density within proper distance of 1Mpc. By comparing high density regions in consecutive redshift bins, we identified the cluster candidates and mapped the large-scale structure within the CFHTLS W2 field.

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