• 천문학회지
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• 제48권1호
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• pp.57-66
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• 2015

Monte-Carlo radiative models of the diffuse Galactic light (DGL) in our Galaxy are calculated using the dust radiative transfer code MoCafe, which is three-dimensional and takes full account of multiple scattering. The code is recently updated to use a fast voxel traversal algorithm, which has dramatically increased the computing speed. The radiative transfer models are calculated with the generally accepted dust scale-height of 0.1 kpc. The stellar scale-heights are assumed to be 0.1 or 0.35 kpc, appropriate for far-ultraviolet (FUV) and optical wavelengths, respectively. The face-on optical depth, measured perpendicular to the Galactic plane, is also varied from 0.2 to 0.6, suitable to the optical to FUV wavelengths, respectively. We find that the DGL at high Galactic latitudes is mostly due to backward or large-angle scattering of starlight originating from the local stars within a radial distance of r < 0.5 kpc from the Earth. On the other hand, the DGL measured in the Galactic plane is mostly due to stars at a distance range that corresponds to an optical depth of $${\sim_\sim}$$ 1 measured from the Earth. Therefore, the low-latitude DGL at the FUV wavelength band would be mostly caused by the stars located at a distance of $r{\leq}0.5$ kpc and the optical DGL near the Galactic plane mainly originates from stars within a distance range of $1{\leq}r{\leq}2kpc$. We also calculate the radiative transfer models in a clumpy two-phase medium. The clumpy two-phase models provide lower intensities at high Galactic latitudes compared to the uniform density models, because of the lower effective optical depth in clumpy media. However, no significant difference in the intensity at the Galactic plane is found.

• 천문학회보
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• 제37권1호
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• pp.73.2-73.2
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• 2012

The far ultraviolet (FUV) wavelength (900-1750A) range includes a wealth of important astrophysical information related to the cooling of hot gas, fluorescent emission from H2 molecules, and starlight scattered off dust particles. Among these, we would like to focus on the scattered emission of the central star by dust with the example of the FUV halo surrounding ${\alpha}$ Vir (Spica). While scattering properties of dust have been studied with the GALEX data, the improved dataset of STSAT-1 revealed many detailed structures of this interesting region. For example, the FUV continuum map obtained from the STSAT-1 observations shows enhanced emission in the southern part of the Spica halo region, where the dust level is also high. In fact, the FUV continuum intensity is seen to have a good correlation with the IRAS 100${\mu}m$ emission data. It is also seen that the scattered spectrum is softer than the original one emitted by the central star, which is attributed to the increase in the dust-scattering albedo with wavelength. We have developed a Monte Carlo code that simulates dust scattering of light including multiple encounters. The code is applied to the present Spica halo region to obtain the scattering properties such as the albedo and the phase function asymmetry factor.

• 천문학회보
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• 제42권2호
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• pp.43.3-43.3
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• 2017

NGC 6822 is a dwarf irregular galaxy in the Local Group and it is located in 500 kpc, further than the Large Magellanic Cloud and the Small Magellanic Cloud. Therefore, we can study star-forming processes by local condition in NGC 6822 instead of tidal force of the Galactic gravitational field. Hubble V is the brightest of several H II complexes in this galaxy. We observed Hubble V by using IGRINS attached on the 2.7 m telescope at the McDonald Observatory in Texas, US in May 2016. We performed a spectral mapping of $15^{{\prime}{\prime}}{\times} 7^{{\prime}{\prime}}$area on H and K bands, and detected emission lines of bright $Br{\gamma}\;{\lambda}2.1661{\mu}m$ and weak He I ${\lambda}2.0587{\mu}m$. Molecular hydrogen lines of 1-0S(1) ${\lambda}2.1218{\mu}m$, 2-1 S(1) ${\lambda}2.2477{\mu}m$, and 1-0 S(0) ${\lambda}2.2227{\mu}m$ was also detected. These emission lines show the structure of an ionized core and excited surface of clouds by far-ultraviolet photons, photodissociation region (PDR). We present three-dimensional maps of emission line distributions through multi slit scanning data and compare these results with the previous study. This presentation shows the physical structure of the star-forming regions and we discuss a PDR model and an evolution of Hubble V complex.

• Journal of Astronomy and Space Sciences
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• 제14권2호
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• pp.259-268
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• 1997

천문대에서 개발 중에 있는 CCD를 사용한 극미 광 영상장비의 시험모델 개발과 현재까지의 결과를 논의하였다. 고도의 저 잡음 도와 안정성이 요구되는 천문관측용 극미 광 영상장비는 자외선에서 가시 광 및 근 적외선 영역에 이르기까지 매우 넓은 파장영역에서 관측을 수행할 수 있는 장비로서 여러 분야에 널리 사용되고 있다. 그러나 현재가지 국내에서는 이 장비의 핵심부분인 controller의 자체설계 기술이 확보되어 있지 않은 실정이다. 이 연구에서 개발된 시스템의 전자 부는 한 개의 EPLD(Erasable Programable Logic Device)에 구현된 controller와, 그 외에 analog driver, video processor로 이루어져 있으며 CCD의 암잡음을 줄이기 위한 방법으로 액체질소 냉각방식을 사용하고 있다. 전체적인 제어와 자료처리는 범용성을 고려하여 개인용 컴퓨터(PC)를 이용하였다. 액체질소 냉각용 cryostat와 CCD 소자를 제외한 대부분이 자체 설계제작 되어진 이 시스템으로 실험실과 소백산천문대에서 시험영상을 얻는데 성공하였다.

• 한국항공우주학회지
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• 제30권6호
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• pp.124-129
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• 2002

한국과학기술원 인공위성연구센터는 우리별 1, 2, 3호의 성공적인 개발 및 발사에 이어 2003년 발사예정으로 과학위성 1호를 개발하고 있다. 과학위성 1호는 주탑재체로 원자외선분광기와 우주플라즈마 관측시스템을 탑재하고 있으며, 우리별 1, 2, 3호의 기술적 유산인 박스형태의 적층식 기계수조로 설계되어 있다. 현재 과학위성 1호는 인증모델의 설계 및 제작과 인증수준의 열진공시험 및 발사환경시험을 성공적으로 마친 상태이다. 본 논문에서는 과학위성 1호 인증모델을 기계구조시스템을 중심으로 소개하고, 발사환경시험 결과를 보고한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.36.2-36.2
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• 2009

We present GALEX (Galaxy Evolution Explorer) far (FUV) and near (NUV) ultraviolet imaging of 34 nearby early-type galaxies from the SAURON representative sample of 48 E/S0 galaxies, all of which have ground-based optical imaging from the MDM Observatory. The surface brightness profiles of nine galaxies (~26 per cent) show regions with blue UV-optical colours suggesting recent star formation. Five of these (~15 per cent) show blue integrated UV-optical colours that set them aside in the NUV integrated colour-magnitude relation. These are objects with either exceptionally intense and localised NUV fluxes or blue UV-optical colours throughout. They also have other properties confirming they have had recent star formation, in particular Hbeta absorption higher than expected for a quiescent population and a higher CO detection rate. This suggests that residual star formation is more common in early-type galaxies than we are used to believe. NUV-blue galaxies are generally drawn from the lower stellar velocity dispersion (sigma_e <200 km/s) and thus lower dynamical mass part of the sample. We have also constructed the first UV Fundamental Planes and show that NUV blue galaxies bias the slopes and increase the scatters. If they are eliminated the fits get closer to expectations from the virial theorem. Although our analysis is based on a limited sample, it seems that a dominant fraction of the tilt and scatter of the UV Fundamental Planes is due to the presence of young stars in preferentially low-mass early-type galaxies.

• 천문학회보
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• 제39권1호
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• pp.61.1-61.1
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• 2014

GSH 006-15+7 is a Milky Way supershell discovered by Moss et al. (2012). This supershell shows large shell-like structures in H I velocity maps. We have analyzed FUV emission for the supershell regions based on the FIMS and GALEX observations. Bright FUV flux at the boundaries of the supershell is mostly originated from dust scattering of FUV photons by dust clouds which was also observed at the boundaries of the supershell. We could find the distance to the supershell can be closer more than 30% compared with the distance of 1500 pc suggested by Moss et al. (2012) from the dust scattering simulation. And we also found the albedo and the phase function asymmetry factor of interstellar grains were 0.30 and 0.40, respectively. The confidence range for the albedo covers the theoretical value of 0.40, but g-factor is rather smaller than the theoretical value of 0.65. The small g-factor might mean the environment of turbulent ISM of the supershell. Meanwhile, the excess of C IV and X-ray emissions in the inside of the supershell can support the existence of hot gas and cooling in the supershell. And the C IV and X-ray emissions are monotonically decrease as away from the center of the SNR. This indicates the size of the hot bubble has considerably shrunk. We applied a simple simulation model to the PDR candidate region of the lower part of the supershell and obtained a H2 column density N(H2) = 1017.0-18.0 cm-2 and total hydrogen density nH ${\geq}$ 10 cm-3. This result shows the PDR candidate region represents a transition region from the warm phase to the cool phase in the PDR.

• 천문학회보
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• 제36권1호
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• pp.88.2-88.2
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• 2011

The far-ultraviolet (FUV) continuum and spectral images of C IV and H2 emission lines for the region of Orion-Eridanus Superbubble (OES) are hereby presented and compared with the maps obtained in other wavelengths. While the region shows complex structures, consisting of hot gases and cold dust, a close examination reveals that the FUV emission in this region can be understood reasonably as the result of their interactions. We confirm the origin of most diffuse FUV continuum to be starlight scattered by dust, but we also find that the ionized gas also contributes 50-70% of the total FUV intensity in the regions of H_alpha arcs. We note the bright diffuse FUV continuum in the eastern part of the northern dust-rich region, and attribute it to the bright early-type stars more abundant in this region than in the west as the amount of dust itself does not seem to be much different across 'arc A' that separates the two regions. In addition, two P Cygni-type stars are identified in this eastern region and their peculiar spectral profiles around the C IV emission line are anifested in the scattered diffuse spectrum. Besides this, the C IV emission is generally enhanced at the boundaries of the hot X-ray cavities where thin dust regions are located, confirming the thermal interface nature of the origin of this cooling emission line. The morphology of the H2 emission shows a general correlation with dust extinction features but its intensity peaks are rather located in thin dust areas, off the peak dust regions. Furthermore, H2 emission is seen to be weak in the arc A region though the arc passes through the center of the dust-rich area. Hence, the H2 emission and dust features, together with those of X-ray and ion lines emissions, show stratified structure of arc A quite well, again confirming its thermal interface nature.

• 천문학회보
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• 제36권1호
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• pp.57.2-57.2
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• 2011

Recent studies find that some early-type galaxies host Type II or Ibc supernovae (SNe II, Ibc). This may imply recent star formation activities in these SNe host galaxies, but a massive star origin of the SNe Ib so far observed in early-type galaxies has been questioned because of their intrinsic faintness and unusually strong Ca lines shown in the nebular phase. To address the issue, we investigate the properties of early-type SNe host galaxies using the data with Galaxy Evolution Explorer (GALEX) ultraviolet photometry and the Sloan Digital Sky Survey optical data. Our sample includes eight SNe II and one peculiar SN Ib (SN 2000ds) host galaxies as well as 32 SN Ia host galaxies. The host galaxy of SN 2005cz, another peculiar SN Ib, is also analyzed using the GALEX data and the NASA/IPAC Extragalactic Database optical data. We find that the NUV?optical colors of SN II/Ib host galaxies are systematically bluer than those of SN Ia host galaxies, and some SN II/Ib host galaxies with NUV - r colors markedly bluer than the others exhibit strong radio emission. We perform a stellar population synthesis analysis and find a clear signature of recent star formation activities in most of the SN II/Ib host galaxies. Our results generally support the association of the SNe II/Ib hosted in early-type galaxies with core collapse of massive stars. We briefly discuss implications for the progenitors of the peculiar SNe Ib 2000ds and 2005cz.

• Journal of Astronomy and Space Sciences
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• 제19권4호
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• pp.283-292
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• 2002

과학위성 1호의 탑재체 원자외선 분광기의 전자보드는 인공위성 운영시 경험하는 환경하에서 전자적 성능을 유지하기 위하여 전자부품의 온도가 지나치게 높아지지 않도록 열적 특성을 고려하여 설계하여야 한다. 이를 위하여 원자외선 분광기의 전자부의 보드수준에서 열 해석을 수행하였고, 원자외선 분광기의 작동환경하에서 전자부품의 허용온도 범위내에서 온도가 유지될 수 있음을 확인하였다.