• 천문학회보
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• 제42권2호
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• pp.86.2-86.2
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• 2017

Blue stragglers (BSs) are the objects that are brighter and bluer than the stars at main-sequence turn-off point. In this study, we present the Ca-by and VI photometry for Galactic dwarf spheroidal galaxies using Subaru/Suprime-Cam and investigate the spatial distribution characteristics of BS stars using the hk index as a photometric metallicity indicator. We compare the cumulative radial distribution of the BS stars with those of two groups of red-giant-branch (RGB) stars divided by the hk-index strength, and find that the spatial distribution of all BS stars is closer to that of hk-weak (i.e. metal-poor) RGB stars. We also find that the hk-strong BS stars are more centrally concentrated than the hk-weak ones. We will discuss the use of hk-index as a metallicity indicator for the hot BS stars and suggest possible explanations for the results in terms of the origin of BS stars in the dwarf gal.

• Journal of Astronomy and Space Sciences
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• 제12권1호
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• pp.1-13
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• 1995

We carried out photometric and spectroscopic observatious of the blue compact dwarf galaxy Haro 6 in the Virgo Cluster of Galaxies. The long-slit spectroscopy was employed at three position angles, $\Phi$=$0^{\circ}$, $\Phi$=$30^{\circ}$, and $\Phi$=$120^{\circ}$with CCD camera mounted on the Cassegrain Spectrograph. Based on the mean intrinsic axial ratio < $q_0$ >=0.3, we derived inclination I of the system as $44^{\circ}$using our composite V-band CCD image. Careful analysis on the velocity field of the system shows an asymptotically fiat rotation curve with the maximum rotational velocity $V(r)_{max}$ reaches about 12km/sec. The calculation of the dynamical mass of Haro 6 with a simple mass model is briefly discussed with emphasis on the mass to luminosity ratio. From the IRAS Point Source Cataloque, we derived dust-to-gas ratio which indicates relatively low dust content, thus tempting us to conjecture the youth of the system.

• 천문학회보
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• 제42권1호
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• pp.48.3-48.3
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• 2017

In our recent investigation of the Oosterhoff dichotomy among globular clusters (GCs), we have shown that the RR Lyrae variables in the Oosterhoff groups I, II, and III are produced mostly by first, second, and third generation stars (G1, G2, and G3), respectively. Unlike GCs, RR Lyrae stars in the Local Group dwarf galaxies show Oosterhoff-intermediate characteristics. The origin of this, however, is yet to be understood. In this poster, we will present our progress in understanding the origin of this phenomenon.

• 천문학회보
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• 제43권1호
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• pp.42.3-42.3
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• 2018

We investigate surface brightness profiles (SBPs) of dwarf galaxies in field, group, and cluster environments. Using images from the Korea Microlensing Telescope Network (KMTNet) Supernova Program (KSP) for the NGC 2784 group and SDSS for the Virgo cluster, SBP types are classified into profiles with single exponential (Type I), double exponential (Type II and Type III). Type II and Type III have smaller and larger outer sizes than inner sizes, respectively. SBP types of field dwarfs are compiled from a previous study. The distributions of SBP types are different in three environments. After comparing sizes of dwarfs in different environments, we suggest that since sizes of some dwarfs are changed due to the environmental effects, SBP types are able to be transformed. It makes that the distributions of SBP types in three environments are different.

• 천문학회보
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• 제36권2호
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• pp.120.2-120.2
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• 2011

최근 북반구 하늘에 대한 SDSS 관측으로부터 우리은하 주변에서 다수 발견된 Ultra-Faint Dwarf Galaxies (uFDs)는 우주의 차가운 암흑물질 (CDM) 이론에서 예측한 질량이 작은 위성은하의 후보로 알려져 있다. 특히 이 uFDs는 역학적 특성과 관련하여 특이한 특징을 갖는 것으로 알려져 있다. 그러나 아직 그 수가 충분하지 않아 더 많은 수의 uFDs의 발견이 기대되고 있다. 이 연구에서는 남반구에서 가동이 시작된 남반구 전천 탐사 망원경 SkyMapper와 향후 가동하게 될 KMT-Net를 이용하여 남반구 하늘에서 SDSS 보다 더 1~2 등급 깊은 관측을 수행하여 다수의 더 어두운 uFDs를 탐색하고, 그 은하와 CDM의 특성을 연구함으로써 우리은하뿐만 아니라 우주의 구조와 진화에서의 CDM의 역할을 규명하는 프로젝트를 제안하려한다. 이 연구에서는 SkyMapper와 KMT-Net의 상호 역할, 관측전략, 기대효과 등 제반사항을 논의하려 한다.

• 천문학회보
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• 제44권1호
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• pp.61.4-61.4
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• 2019

The key science goal of the KMTNet Supernova Program (KSP) is to detect and study the early explosions of supernovae using one fifth of the KMTNet time. The BVI-band observations of the nearby target fields mostly closer than 30 Mpc distance and the follow-up spectroscopy provide valuable information on the early phase of the supernovae. These data can also be used for the studies of optical transients such as novae, dwarf novae, variable stars, and active galactic nuclei. Stacked images of several hundred images obtained from the time domain observations can be used for the search of low surface brightness galaxies reaching $28mag\;arcsec^{-2}$. Results and status of the KSP including ${\geq}20$ infant supernovae and ${\geq}100$ faint dwarf galaxies will be presented in this talk.

• 천문학회보
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• 제24권2호
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• pp.115-115
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• 1999

• 천문학회보
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• 제24권2호
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• pp.116-116
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• 1999

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1999년도 한국우주과학회보 제8권2호
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• pp.40-40
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• 1999

No Abstract, See Full Text

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1999년도 한국우주과학회보 제8권2호
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• pp.111-111
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• 1999

No Abstract, See Full Text