• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.61.1-61.1
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• 2012

We examine both optical and optical/near-infrared (NIR) color distributions of the globular cluster (GC) system in the core of the Coma cluster of galaxies (Abell 1656), centered on the giant elliptical galaxy NGC 4874, to study how non-linearities in the color-metallicity relations of GC systems in large elliptical galaxies are linked to bimodal optical color distributions. Since optical-NIR color distributions of extragalactic GC systems reflect the underlying features of the metallicity distributions, we also present the color-color relation for this GC system. In order to do this, we combine F160W ($H_{160}$) NIR imaging data acquired with the Wide Field Camera 3 IR Channel (WFC3/IR), newly installed on Hubble Space Telescope (HST), with F475W ($g_{475}$) and FF814W ($I_{814}$) optical imaging data from the HST Advanced Camera for Surveys (ACS). To quantitatively explain the feature of color distributions, we use the Gaussian Mixture Modeling (GMM) code. Finally, we show the radial distribution of the GCs in the field of NGC 4874.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.283-287
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• 2015

Within the context of the hugely successful SAGE-LMC and SAGE-SMC surveys, Spitzer photometry observations of the Large and Small Magellanic Clouds have revealed millions of infrared point sources in each galaxy. The brightest infrared sources are generally dust producing and mass-losing evolved stars, and several tens of thousands of such stars have been classified. After photometrically classifying these objects, the dust production by several kinds of evolved stars - such as Asymptotic Giant Branch stars and Red Supergiants - can be determined. SAGE-Spec is the spectroscopic follow-up to the SAGE-LMC survey, and it has obtained Spitzer-IRS $5-40{\mu}m$ spectroscopy of about 200 sources in the LMC. Combined with archival data from other programs, observations at a total of ~1000 pointings have been obtained in the LMC, while ~250 IRS pointings were observed in the SMC. Of these, a few hundred pointings represent dust producing and mass-losing evolved stars, covering a range in colors, luminosities, and thus mass-loss rates. Red Supergiants and O-rich and C-rich AGB stars - the main dust producers - are well represented in the spectroscopic sample. This paper will summarize what we know about the mineralogy of dust producing evolved stars, and discuss their relative importance in the total dust budget.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.341-343
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• 2015

We present an analysis of the relation between star-formation (SF) and accretion luminosities of local type-2 active galactic nuclei (AGNs) at $0.01{\leq}z<0.22$. We match type-2 AGNs found in the Sloan Digital Sky Survey to current far-infrared (FIR) survey catalogues based on AKARI and Herschel. Estimating AGN luminosities from [$O{\small{III}}$]${\lambda}5007$ and [$O{\small{I}}$]${\lambda}6300$ emission lines, we find a positive linear trend between FIR and AGN luminosities over a wide dynamical range. This result appears to be inconsistent with recent reports that low-luminosity AGNs show no correlation between FIR and X-ray luminosities; this contradiction is likely due to Malmquist and sample selection biases. Moreover, we also find that pure-AGN candidates, for which the FIR radiation is thought to be AGN-dominated, show significant low-SF activities. These AGNs hosted by low-SF galaxies are rare in our sample. However, it is possible that the low fraction of low-SF AGN is caused by observational limitations, as recent FIR surveys are not sufficient to examine the population of high-luminosity AGNs hosted by low-SF galaxies.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.667-669
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• 2003

A bio-optical model was developed specific for turbid and shallow waters. Special studies were carried out to estimate absorption and scattering properties as well as backscattering probability of suspended matter. The inversion of bio-optical model allows for direct retrieval of turbidity and chlorophyll- a from the visible-near infrared (VNIR) range sensor. Time-series satellite imagery from ASTER AM-1 sensor, were used to monitor the Laguna de Bay water quality condition. Spatial distribution of temperature for the lake was extracted from the thermal infrared (TIR) sensor. Corresponding field surveys were conducted to parameterize the bio -optical model. In-situ measurements include suspended particle and chlorophyll-a concentrations profiles from nephelometric devices and processing of water samples. Hyperspectral measurements were used to validate results of the bio -optical model and satellite- based estimation. This study provides a theoretical basis and a practical illustration of applying space- based measurements on an operational basis.

• 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.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.149-150
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• 2012

We have created new catalogues of AKARI/IRC $2-24{\mu}m$ North Ecliptic Pole Deep survey through new methods of image analysis. In the new catalogues the number of false detection decreased by a factor of 10 and the number of objects detected in multiple bands increased by more than 1,500 compared to the previous work. In this proceedings the new methods of image analysis and the performance of the new catalogues are described.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.289-290
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• 2012

Feedback from accreting BH (AGN) is thought to be responsible for the co-evolution of BHs and galaxies. It is likely to be prominent in the most luminous dust-obscured quasars, particularly those containing radio sources too luminous to be powered by starbursts. In order to investigate the feedback mechanism in detail, we select a unique sample containing ~ 200 of the most luminous obscured QSOs by cross-matching the WISE catalog with the FIRST and NVSS radio surveys. We present overall statistics for the observed range of colors and radio/mid-IR flux density ratio. We also present our efforts to understand the physical and evolutionary nature of these extreme feedback candidates using various telescopes such as Magellan, SOAR, Herschel, and ALMA.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.58.1-58.1
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• 2013

We present $10{\mu}m-35{\mu}m$ Spitzer spectra of the interstellar medium in the Central Molecular Zone (CMZ), the central 210 pc ${\times}$ 60 pc of the Galactic center (GC). We present maps of the CMZ in ionic and $H_2$ emission, covering a more extensive area than earlier spectroscopic surveys in this region. The radial velocities and intensities of ionic lines and $H_2$ suggest that most of the $H_2$ 0-0 S(0) emission comes from gas along the line-of-sight, as found by previous work. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby Galaxies Survey (SINGS) to our data. Previous work shows that forbidden line ratios can distinguish star-forming galaxies from LINERs and AGNs. Our GC line ratios agree with star-forming galaxies and not with LINERs or AGNs.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.28.4-28
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• 2001

This paper proposes an IR camera system that performs the task of removing mines for humanitarian purposes. Because of the high risks involved, it is necessary to conduct mine detection from the most remote endeavoring. By mating use of infrared ray (IR) cameras, scattered mines can be detected from remote locations. In the case of mines buried in the ground, detection is possible if the peripheral temperature difference is large enough between the ground and mine weapon. As one of the world´s advanced nations in sensor technology, Japan should promote surveys and studies for detecting mines safely by using its advanced remote sensing technologies.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.36.1-36.1
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• 2018

Star formation activity of galaxies, along with color and morphology, show significant environmental dependence in local universe, where galaxies in dense environment tend to be more quiescent and redder. However, many studies show that such environmental dependence does not continue at higher redshifts beyond z~1. The question of how the environmental dependence of galactic properties have developed over time is crucial to understanding cosmic galactic evolution. By combining data from Canada-France-Hawaii Telescope Legacy Survey(CFHTLS), Infrared Medium-Deep Survey(IMS), and other surveys, the photometric redshifts of galaxies in CFHTLS W2 field were estimated by fitting spectral energy distribution. The distribution of galaxies was mapped in redshift bins of 0.05 interval from 0.6 to 1.4. For each redshift bin, the number density was mapped. The galaxies in high density regions were grouped into clusters using friend-of-friend method. The color of galaxies were analyzed to study the correlation with redshift as well as environmental difference between field galaxies and cluster member galaxies.