• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.98.2-98.2
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• 2012

We firstly present the unified Far-UV continuum map of the Taurus-Auriga-Perseus (TPA) complex, one of the largest local associations of dark cloud located in (l, b)=([154,180], [-28, -2]), by merging both FIMS and GALEX. The FUV continuum map shows that dust extinction correlate well with the FUV around the complex. It shows strong absorption in FUV toward the dense Taurus cloud while it does not in California cloud. It turned out that it is related to the relative location of each cloud and Perseus OB2 association. We also present some results of dust scattering simulation based on Monte Carlo Radiative Transfer technique (MCRT). Through this dust scattering simulation, we have derived the scattering parameter for this region, albedo(a)=$0.42^{+0.05}{_{-0.05}}$, asymmetry factor(g)=$0.47^{+0.11}{_{-0.27}}$. The optical parameters we obtained seem reasonable compared to the theoretical model values ~0.40 and ~0.65 for the albedo and the phase function though the phase function is rather small. Using the result of simulation, we figured out the geometries of each cloud in the complex region, especially their distances and thicknesses. Our predictions from the results are in good agreement with the previous studies related to the TPA complex. For example, the Taurus cloud is within ~200pc from the Sun and the Perseus seems to be multi-layered, at least two. The California cloud is more distant than the other cloud on average at ~350 pc and Auriga cloud seems to be between the Taurus cloud and the eastern end of the California cloud. We figured out that across the TPA complex region, there might be some correlation between the LSR velocity and the distance to each cloud in the complex.

• Journal of Astronomy and Space Sciences
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• v.18 no.1
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• pp.81-93
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• 2001

Far ultraviolet IMaging Spectrograph (FIMS) should be designed to maintain its structural stability and to minimize optical performance degradation in launch and in operation enviroments. The structural and thermal analyzes of grating and grating mount system, which are directly related to FIMS optical performance, was performed using finite element method. The grating mount was made to keep the grating stress down, while keeping the natural frequency of the grating mount higher than 100 Hz. Transient and static thermal analyzes were also performed and the results shows that the thermal stress on the grating can be attenuated sufficiently. The optical performance variation due to temperature variation was with the allowed range.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.3 no.1
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• pp.41-56
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• 1999

Since UV-B radiation measuring networks have not been established, numerical models which calculate the flux from other readily available meteorological measurements may play an important role. That is, such a problem can be solved by using parameterization models such as two stream approximation, the delta-Eddington method, doubling method, and discrete ordinate method. However, most UV-B radiative transfer models have not been validated with measurements, because such models are not intended as practical computational schemes for providing surface estimates of UV-B radiation. The main concern so far has been to demonstrate model sensitivity for cloudless skies. In particular, few have been concerned with real cloud information. Clouds and aerosols have generally been incorporated as constituents of particular atmospheric layers with specified optical depths and scattering properties. The parameterization model presented here is a combination of a detailed radiative transfer algorithm for a coludless sky radiative process and a more approximate scheme to handle cloud effects. The model input data requires a daily measurement of the total ozone amount plus a daily record of the amount and type of cloud in the atmosphere. Measurements for an examination of the models at the Department of Atmospheric Sciences, Pusan National University have been takenfrom February, 1995. These models can be used to calculate present and future fluxes where measurements have not been taken, and construct climatologies for the period before ozone depletion began.

• Journal of Astronomy and Space Sciences
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• v.17 no.1
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• pp.67-76
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• 2000

Far-ultraviolet IMaging Spectrograph(FIMS) is the main payload of the first Korean scientific satellite, KAISTSTA-4, which will be launched in 2002. The optical system of FIMS consists of parabolic cylinder mirror, slit, ellipsoidal reflection grating, and MCP to get spatial information as well as spectral information. Allowed ranges of manufacturing and positioning error are derived for each optical components to achieve the astronomical goals. In the procedure, graphical simplification is dedicated to understand sensitivity table and to derive range and precision of manipulation for each optical component. The result shows that precision of ${\mu}m$ for linear and of 2' for angular manipulation fulfills optical requirements.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.40.1-40.1
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• 2016

We present the far-ultraviolet fluorescent molecular hydrogen ($H_2$) emission map observed with FIMS/SPEAR for ~76% of the sky. The fluorescent $H_2$ emission is found to be saturated by strong dust extinction at the optically thick, Galactic plane region. However, the extinction-corrected intensity of fluorescent $H_2$ emission is found to have strong linear correlations with the well-known tracers of the cold interstellar medium, such as the E(B-V) color excess, neutral hydrogen column density N(HI), $H{\alpha}$ emission, and CO $J=1{\rightarrow}0$ emission. The all-sky molecular hydrogen column density map is also obtained using a photodissociation region model. We also derive the gas-to-dust ratio, hydrogen molecular fraction ($f_{H2}$), and $CO-to-H_2$ conversion factor ($X_{CO}$) of the diffuse interstellar medium. The gas-to-dust ratio is consistent with the standard value $5.8{\times}10^{21}atoms\;cm^{-2}mag^{-1}$, and the $X_{CO}$ tends to increase with E(B-V), but converges to the Galactic mean value $1.8{\times}10^{20}cm^{-2}K^{-1}km^{-1}s$ at optically thick regions with E(B-V)>2.0.

• Publications of The Korean Astronomical Society
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• v.18 no.1
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• pp.87-95
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• 2003

FIMS (Far-ultraviolet IMaging Spectrograph) is the main payload of STSAT-1 satellite which was successfully launched on September 27, 2003. The optical system of FIMS consists of two sets of parabolic cylinder mirror, slit, ellipsoidal reflection grating, and baffle system. We designed two types of baffle system for the FIMS: FOV baffle and order baffle. FOV baffle in the mirror house controls the field of view, and the order baffle in the vacuum box blocks the rays reflected rays by different orders.

• Journal of The Korean Astronomical Society
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• v.31 no.1
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• pp.51-65
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• 1998

We present B VRI CCD surface photometry for the central $(6'.35\times6'.35)$ regions of the dwarf elliptical galaxies NGC 185 and NGC 205 in the Local Group. Surface brightness profiles of NGC 185 (R<225') and NGC 205 (R<186') show excess components in the central regions. The colors of NGC 185 get bluer inward at R<25', while they remain constant at $R\geq25'$. The colors of NGC 205 get bluer inward at 1'$\approx10^5\; L_\bigodot$. Distributions of dust clouds in the central regions of the two galaxies are also investigated.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.11-20
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• 2005

We present measurements of interstellar $H_2$ absorption lines in the continuum spectra of 54 early-type stars in the Galactic disk and halo and 3 stars in the Magellanic Clouds. The data were obtained with the Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS), part of the ORFEUS telescope, which flew on the ORFEUS-SPAS I and II space-shuttle missions in 1993 and 1996, respectively. The spectra extend from the interstellar cutoff at $912{\AA}$ to about $1200{\AA}$ with a spectral resolution of ${\sim}3000$ and statistical signal-to-noise ratios between 10 and 65. Assuming a velocity profile derived from optical observations (when available), we model the column densities N(J) of the rotational levels J = 0 through 5 for each line of sight. Our data reproduce the relationships among molecular and total hydrogen column density, fractional molecular abundance, and reddening first seen in Copernicusobservations of nearby stars (Savage et al. 1977). The results show that most of these molecular clouds have $H_2$ total column densities between $10^{15}cm^{-2}$ and $10^{21}cm^{-2}$, and kinetic temperatures from 21 K to 232 K, with average of 89 K, consistent with the result of Copernicus (Savage et al. 1977).

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.216-224
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• 1997

We present IUE observations in far ultraviolet region for SS Lac in open cluster NGC 7209. The IUE short wavelength spectrum and long wavelength spectrum were merged to produce an energy distribution curve between $1200{AA}$ and $3200{AA}$. The curve has been unreddened to take out reddening effect. Then the surface temperature, gravity and abundance of SS Lac were determined based on the Kurucz model atmosphere. The photographic light curve produced before cessation of eclipse were analyzed for photometric solutions. We confirmed SS Lac is a member of open cluster NGC 7209 based on its possible distance. The main reason for the cessation of eclipse is the change of the system's orbital inclination rather than collisional merge of two stars.

• Journal of Astronomy and Space Sciences
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• v.30 no.1
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• pp.59-67
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• 2013

We present a spectroscopic study of 343 blue compact galaxies (BCGs) at 0.20 < z < 0.35 from the Sloan Digital Sky Survey (SDSS) DR7 data. We derive gas phase oxygen abundance using the empirical and direct method. Stellar masses of galaxies are derived from the STARLIGHT code. We also derive star formation rates of galaxies based on $H{\alpha}$ emission line from the SDSS as well as far-ultraviolet (FUV) flux from the Galaxy Evolution Explorer GR6 data. Evolution of the luminosity-metallicity and mass-metallicity (M-Z) relations with redshift is observed. At a given luminosity and mass, galaxies at higher redshifts appear to be biased to low metallicities relative to the lower redshift counterparts. Furthermore, low mass galaxies show higher specific star formation rates (SSFRs) than more massive ones and galaxies at higher redshifts are biased to higher SSFRs compared to the lower redshift sample. By visual inspection of the SDSS images, we classify galaxy morphology into disturbed or undisturbed. In the M-Z relation, we find a hint that morphologically disturbed BCGs appear to exhibit low metallicities and high SSFRs compared to undisturbed counterparts. We suggest that our results support downsizing galaxy formation scenario and star formation histories of BCGs are closely related with their morphologies.