Il-Joong Kim

OBSERVATION OF THE FAR-ULTRAVIOLET CONTINUUM BACKGROUND WITH SPEAR/FIMS

We present the general properties of the far-ultraviolet (FUV; 1370-1710 A) continuum background over most of the sky, obtained with the Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR) instrument (also known as FIMS), flown aboard the STSAT-1 satellite mission. We find that the diffuse FUV continuum intensity is well correlated with N H I , 100 μm, and Hα intensities but anti-correlated with soft X-ray intensity. The correlation of the diffuse background with the direct stellar flux is weaker than the correlation with other parameters. The continuum spectra are relatively flat. However, a weak softening of the FUV spectra toward some sight lines, mostly at high Galactic latitudes, is found not only in direct stellar but also in diffuse background spectra. The diffuse background is relatively softer than the direct stellar spectrum. We also find that the diffuse FUV background averaged over the sky has a bit softer spectrum compared to direct stellar radiation. A map of the ratio of 1370-1520 A to 1560-1710 A band intensity shows that the sky is divided into roughly two parts. However, this map shows a lot of patchy structures on small scales. The spatial variation of the hardness ratio seems to be largely determined by the longitudinal distribution of OB-type stars in the Galactic plane. A correlation of the hardness ratio with the FUV intensity is found at high intensities but an anti-correlation is found at low intensities. We also find evidence that the FUV intensity distribution is log-normal in nature.

DIFFUSE EXTRAPLANAR DUST IN NGC 891

We report the detection of vertically extended far-ultraviolet and near-UV emissions in an edge-on spiral galaxy NGC 891, which we interpret as being due to dust-scattered starlight. Three-dimensional radiative transfer models are used to investigate the content of the extraplanar dust that is required to explain the UV emission. The UV halos are well reproduced by a radiative transfer model with two exponential dust disks, one with a scale height of ≈0.2-0.25 kpc and the other with a scale height of ≈1.2-2.0 kpc. The central face-on optical depth of the geometrically thick disk is found to be at the B band. The results indicate that the dust mass at |z| > 2 kpc is ≈3%-5% of the total dust mass, which is in good accordance with the recent Herschel submillimeter observation. Our results, together with the recent discovery of the UV halos in other edge-on galaxies, suggest the widespread existence of a geometrically thick dust layer above the galactic plane in spirals.

COMPARISON OF THE DIFFUSE Hα AND FUV CONTINUUM BACKGROUNDS: ON THE ORIGINS OF THE DIFFUSE Hα BACKGROUND

We compare the diffuse H

Conceptual Design of the NISS onboard NEXTSat-1

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Far-Ultraviolet Observations of the Monogem Ring

map of our Galaxy with the FUV (1370-1710\AA) continuum map. The H

GLOBAL FAR-ULTRAVIOLET PROPERTIES OF THE CYGNUS LOOP

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FAR-ULTRAVIOLET COOLING FEATURES OF THE ANTLIA SUPERNOVA REMNANT

intensity correlates well with the FUV intensity. The H

Far-ultraviolet Spectral Images of the Vela Supernova Remnant: Supplements and Comparisons with Other Wavelength Images

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Thermal Analysis of MIRIS Space Observation Camera for Verification of Passive Cooling

/FUV intensity ratio increases in general with the H

FAR-ULTRAVIOLET EMISSION-LINE MORPHOLOGIES OF THE SUPERNOVA REMNANT G65.3+5.7

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