• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.48.1-48.1
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• 2012

We present the ultraviolet (UV) color-color relation of early-type galaxies (ETGs) in the nearby universe (0.05 < z < 0.12) to investigate the properties of hot stellar populations responsible for the UV excess (UVX). The initial sample of ETGs is selected by the spectroscopic redshift and the morphology parameter from the SDSS DR 7, and then cross-matched with the GALEX far-UV (FUV) and near-UV (NUV) GR6 data. The cross-matched ETG sample is further classified by their emission line characteristics in the optical spectra into quiescent, star-forming, and active galactic nucleus categories. Contaminations from early-type spiral galaxies, mergers, and morphologically disturbed galaxies are removed by visual inspection. By drawing the FUV-NUV (as a measure of UV spectral shape) versus FUV-r (as a measure of UVX strength) diagram for the final sample of -3700 quiescent ETGs, we find that the "old and dead" ETGs consist of a well-defined sequence in UV colors, the "UV red sequence," so that the stronger UVX galaxies should have a harder UV spectral shape systematically. However, the observed UV spectral slope is too steep to be reproduced by the canonical stellar population models in which the UV flux is mainly controlled by age or metallicity parameters. Moreover, 2 mag of color spreads both in FUV-NUV and FUV-r appear to be ubiquitous among any subsets in distance or luminosity. This implies that the UVX in ETGs could be driven by yet another parameter which might be even more influential than age or metallicity.

• The Journal of Korean Philosophical History
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• no.43
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• pp.267-293
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• 2014

This paper is aimed at analyzing the characteristics of Image-Meaning theory focused on image in the early days of the Joseon Dynasty and SongMing period. Zhouyi' theory in the early days of the Joseon Dynasty was constructed on the basis of Zhouyi' theory of SongMing period. The characteristics of Image-Meaning theory in the early days of the Joseon Dynasty can be explained largely by two routes. One is the perspective of critical succession on Zhouyi'theory of focusing on meaning that led Chengyi(程?) and Yangwanli(楊萬裏). As the representative of this route, Gwongeun and Toegye not only asserted Image-meaning theory focused on meaning, but also developed a perspective of taking all the image and meaning. The other is the active succession and creative transformation about Image-Meaning theory of Tushuxue that led Chentuan(陳?) and Shaoyong(邵雍). As the representative of that route, Yulgok and Yeohun explained the schematic diagram of the universe of the universe by using methodology of Tushuxue. Furthermore, they actively succeed Shaoyong' Zhouyi theory to expand Image-Meaning theory focused on number. In addition, Cho, Haoyi(曺好益)described the propositions - "meaning is not out of image area, image equipped with meaning all, then there is no law of limitation in image adopted theory. Those propositions are opposed to Chengyi(程?) and Zhuxi(朱熹)' ZhouYi' theory.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.179-182
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• 2005

We conducted an extremely wide field survey of z ${\~}$ 6 Lyman break galaxies (LBGs) to precisely derive their bright end surface density overcoming the bias due to cosmic variance. We selected out LBG candidates in the Subaru/ XMM-Newton Deep Survey Field (SXDS) over the total of ${\~}1.0\;deg^2$ sky area down to $z_{AB} = 26.0 ({\ge}3{\sigma},\;2'.0 aperture)$ using i' - z' > 1.5 color cut. This sample alone is likely to be contaminated by M/L/T dwarfs, low-z elliptical galaxies, and z ${\~}$ 6 quasars. To eliminate these interlopers, we estimated their numbers using an exponential disk star count model, catalogs of old ellipticals in the SXDS and other field, and a z${\~}$6 quasar luminosity function. The finally derived surface density of z ${\~}$ 6 LBGs was 165 $mag^{-1}\;deg^{-2}$ down to $z_{AB}$ = 26.0 and shows good agreement with previous results from the narrower field survey of HST GOODS.

• Journal of The Korean Astronomical Society
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• v.35 no.4
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• pp.175-185
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• 2002

Almost half of primeval galaxies show P-Cygni type profiles in the Ly$\alpha$ emission line. The main underlying mechanism for the profile formation in these systems is thought to be the frequency re-distribution of the line photons in expanding scattering media surrounding the emission source. A Monte Carlo code is developed to investigate the Ly$\alpha$ line transfer in an optically thick and moving medium with a careful consideration of the scattering in the damping wings. Typical column densities and expansion velocities of neutral hydrogen investigated in this study are $N_{H1}{\~}10^{17-20}\;cm^{-2}$ and ${\Delta}V{\~} 100 km\;s^{-1}$. We investigate the dependence of the emergent profiles on the kinematics and on the column density. Our numerical results are applied to show that the damped Ly$\alpha$ absorbers may possess an expanding H I supershell with bulk flow of ${\~}200 km\;s^{-l}$ and H I column density $N_{H1}{\~}10^{19}\;cm^{-2}$. We briefly discuss the observational implications.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.83.2-83.2
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• 2013

Camera for QUasars in EArly uNiverse (CQUEAN) is an optical CCD camera developed by the Center for the Exploration of the Origin of the Universe (CEOU). In 2010 August, CQUEAN was attached on the 2.1m Otto Struve Telescope at the McDonald Observatory in Texas, USA. As the main purpose of CQUEAN is detecting the Lyman breaks of redshift ~5 quasars, it is sensitive to near-infrared wavelengths (0.7-1.0 ${\mu}m$). For the auto-guiding system, it is using a rotating guide arm to find guide stars on the Cassegrain off-axis focus of the telescope. We plan to upgrade a new filter wheel system consists of a series of narrow band filters. We will install this independent auto-guiding units on the finder scope, which makes rooms on the Cassegrain focal plane of the main telescope. In this presentation we present the system architecture of the CQUEAN Auto-guiding Package (CAP).

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.141-145
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• 2009

Lee Sang, a poet and a architect, made new experimental poems that was influenced by quantum mechanics and theory of relativity that were published in the early 1900's, and he showed his new view of the world that transcended time and space limit through his poems. In this essay, I studied and analyzed on the links between his view of the world and modern design view with as the central figure his text, 'A Written Promise of The Line' The result is that he fellow the cyclic world view which the world consisted of cycles within cycles, of immense duration and the scientific view of the world which the universe and me are one flesh.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.61.1-61.1
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• 2014

IC 10 is one of the most well-known irregular starburst dwarf galaxies in the Local Group. Its low metal and oxygen abundance together with proximity make it an excellent laboratory to test star formation models, especially in low-metallicity systems like galaxies in the early Universe as well as many other local dwarfs. Among a number of active star forming regions, we have detected H2O kilo-maser emission in the south-east region of IC 10(IC 10 SE) using the Korean VLBI Network(KVN). This maser line is likely to be associated with a giant molecular cloud identified in IC 10 SE by former CO studies. Using the HI and CO data from the VLA and SMA archive, we probe the atomic and molecular gas properties of IC 10 SE. We discuss how the cool gas morphology and kinematics are related with maser and star formation activity in IC 10 SE.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.39.1-39.1
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• 2010

We are developing a CCD camera named CQUEAN (Camera for Quasars in Early Universe) to search for quasars at z > 7. CQUEAN has a 1024*1024 deep depletion CCD chip and will be attached to 2.1m Otto-Struve Telescope at McDonald Observatory, USA. Although commercial software for the CCD camera is provided by the vendor, we are going to develop our own software to control the other instruments as well, to carry out efficient observation. There are four major parts in our software: Instrument control part controls the camera and filter wheel to obtain imaging data. Quick look window is to display acquired imaging data for quick inspection. Telescope control part interfaces with Telescope Control System (TCS) to move the telescope and to get time or coordinate information. Finally, Observation scripting facility part carries out a series of short exposures in a batch. The whole software will be written in python on linux platform, using the instrument control software libraries provided by the vendors.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.82.1-82.1
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• 2010

We have investigated the spatial configuration of stars within the tidal radius of metal poor globular cluster NGC 6626 in the bulge direction. Data were obtained in near-IR J,H,Ks bands with wide-field ($20'\times20'$) detector, WIRCam at CFHT. To trace the stellar density around target cluster, we sorted cluster's member stars by using a mask filtering algorithm and weighting the stars on the color-magnitude diagram. From the weighted surface density map, we found that the stellar spatial distributions within the tidal radius appear asymmetric and distorted features. Especially, we found that more prominent over-density features are extending toward the direction of Galactic plane rather than toward the directions of the Galactic center and its orbital motion. This orientation of the stellar density distribution can be interpreted with result of disk-shock effect of the Galaxy that the cluster had been experienced. Indeed, this over-density feature are well represented in the radial surface density profile for different angular sections. As one of the metal poor globular clusters with extended horizontal branch (EHB) in the bulge direction, NGC 6626 is kinematically decoupled from the normal clusters and known to have disk motion of peculiar motion. Thus, our result will be able to add further constraints to understand the origin of this cluster and the formation of bulge region in early universe.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.25.3-25.3
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• 2009

To search for the quasars at z > 7 in early universe, we are developing a optical camera which has a $1k\times1k$ deep depletion CCD chip, with later planned upgrade to HAWAII-2RG infrared array. We are going to attach the camera to the cassegrain focus of Otto Struve 2.1m telescope at McDonald observatory of University of Texas at Austin, USA. We present the design of a hardware interface to attach the CCD camera to the telescope. It consists of focal reducer, filter wheel, and guiding camera. Focal reducer is needed to reduce the long f-ratio (f/13.7) down to about 4 for wide field of view. The guiding camera design is based on that of DIAFI offset guider which developed for the McDonald 2.7m telescope.