• The Bulletin of The Korean Astronomical Society
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• v.30 no.2
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• pp.51.2-51.2
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• 2005

• The Bulletin of The Korean Astronomical Society
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• v.20
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• pp.32.1-32.1
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• 1995

• The Bulletin of The Korean Astronomical Society
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• v.18
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• pp.10-11
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• 1993

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.141-141
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• 2008

• The Bulletin of The Korean Astronomical Society
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• v.33 no.2
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• pp.81.1-81.1
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• 2008

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.237-242
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• 2012

We have performed a systematic study of interstellar dust grains in various environments of galaxies. AKARI has revealed the detailed properties of dust grains not only in star-forming regions but also in regions not relevant to star formation, some of which are found not to follow our old empirical knowledge. Because of its unique capabilities, AKARI has provided new knowledge on the processing of large grains and polycyclic aromatic hydrocarbons (PAHs). For example, we detect PAHs from elliptical galaxies, which show unusual spectral features and spatial distributions, demonstrating importance of material processing in the interstellar space. We find that copious amounts of large grains and PAHs are flowing out of starburst galaxies by galactic superwinds, which are being shattered and destroyed in galactic haloes. We discover evidence for graphitization of carbonaceous grains near the center of our Galaxy, providing a clue to understanding the activity of the Galactic center. We review the results obtained from our AKARI program, focusing on the processing of carbonaceous grains in various environments of galaxies.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.11-15
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• 2017

We present the AKARI far-infrared (FIR) all-sky maps and describe its characteristics, calibration accuracy and scientific capabilities. The AKARI FIR survey has covered 97% of the whole sky in four photometric bands, which cover continuously 50-180 micron with band central wavelengths of 65, 90, 140, and 160 microns. The data have been publicly released in 2014 (Doi et al., 2015) with improved data quality that have been achieved since the last internal data release (Doi et al., 2012). The accuracy of the absolute intensity is ${\leq}10%$ for the brighter regions. Quantitative analysis of the relative intensity accuracy and its dependence upon spatial scan numbers has been carried out. The data for the first time reveal the whole sky distribution of interstellar matter with arcminute-scale spatial resolutions at the peak of dust continuum emission, enabling us to investigate large-scale distribution of interstellar medium in great detail. The filamentary structure covering the whole sky is well traced by the all-sky maps. We describe advantages of the AKARI FIR all-sky maps for the study of interstellar matter comparing to other observational data.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.243-248
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• 2004

We present measurements of interstellar CO absorption lines in the spectra of 7 early-type stars that were observed with the FUSE(Far Ultraviolet Spectroscopic Explore.) Among 54 early-type target stars in the Galactic disk and halo observed with the BBFS(Berkeley Extreme and Far-ultraviolet Spectrometer), we choose 7 program stars (HD 37903, HD 97991, HD 149881, HD 156110, HD 164794, HD 214080 and HD 219188) which have only a single velocity component in the high-resolution optical measurements, in order to avoid line blending. To analyze the CO molecule, we select the E-X (0-0) band at $1076{\AA}$, which has a large oscillate. strength and is not blended with other interstellar absorption lines. We detect the CO absorption lines in three (HD 37903, HD 164794, and HD 214080) out of seven targets, and derive CO column densities for those targets. We also estimated the CO to $H_2$ ratios toward the three stars, based on the previously estimated $H_2$ column densities.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.171-172
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• 1996

We present the results of an rocket-borne observation of far-infrared [CII] line at 157.7 ${\mu}m$ from the diffuse inter-stellar medium in the Ursa Major. We also introduce a part of results on the [CII] emission recently obtained by the IRTS, a liquid-helium cooled 15cm telescope onboard the Space Flyer Unit. From the rocket-borne observation we obtained the cooling rate of the diffuse HI gas due to the [CII] line emission, which is $1.3{\pm}0.2 {\times} 10^{-26}$ $ergss^{-1} H^{-1}_{atom}$. We also observed appreciable [CII] emission from the molecular clouds, with average CII/CO intensity ratio of 420. The IRTS observation provided the [CII] line emission distribution over large area of the sky along great circles crossing the Galactic plane at I = $50^{\circ}$ and I = $230^{\circ}$. We found two components in their intensity distributions, one concentrates on the Galactic plane and the another extends over at least $20^{\circ}$ in Galactic latitude. We ascribe one component to the emission from the Galactic disk, and the another one to the emission from the local interstellar gas. The [CII] cooling rate of the latter component is $5.6 {\pm} 2.2 {\times}10$.

• Journal of The Korean Astronomical Society
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• v.34 no.4
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• pp.309-311
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• 2001

Strong thermal X-ray emission, called Galactic Ridge X-ray Emission, is observed along the Galactic plane (Koyama et al. 1986). The origin of hot ($\~$7 keV) component of GRXE is not known, while cool ($\~$0.8 keV) one is associated with supernovae (Kaneda et al. 1997, Sugizaki et al. 2001). We propose a possible mechanism to explain the origin; locally strong magnetic fields of $B_{local}\;\~30{\mu}G$ heat interstellar gas to $\~$7 keV via magnetic reconnection (Tanuma et al. 1999). There will be the small-scale (< 10 pc) strong magnetic fields, which can be observed as $(B)_{obs} \;\~3{\mu}G$ by integration of Faraday Rotation Measure, if it is localized by a volume filling factor of f $\~$ 0.1. In order to examine this model, we solved three-dimensional (3D) resistive magnetohydrodynamic (MHD) equations numerically to examine the magnetic reconnect ion triggered by a supernova shock (fig.l). We assume that the magnetic field is Bx = 30tanh(y/20pc) $\mu$G, By = Bz = 0, and the temperature is uniform, at the initial condition. We put a supernova explosion outside the current sheet. The supernova-shock, as a result, triggers the magnetic reconnect ion, and the gas is heatd to > 7 keV. The magnetic reconnect ion heats the interstellar gas to $\~$7 keV in the Galactic plane, if it occurs in the locally strong magnetic fields of $B_{local}\;\~30{\mu}G$. The heated plasma is confined by the magnetic field for $\~10^{5.5} yr$. The required interval of the magnetic reconnect ions (triggered by anything) is $\~$1 - 10 yr. The magnetic reconnect ion will explain the origin of X-rays from the Galactic ridge, furthermore the Galactic halo, and clusters of galaxies.