• 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.32 no.1
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• pp.25-27
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• 2017

We are creating all-sky diffuse maps from the AKARI mid-infrared survey data with the two photometric bands centered at wavelengths of 9 and $18{\mu}m$. The AKARI mid-infrared diffuse maps achieve higher spatial resolution and higher sensitivity than the IRAS maps. In particular, the $9{\mu}m$ data are unique resources as an all-sky tracer of the emission of polycyclic aromatic hydrocarbons (PAHs). However, the original data suffer many artifacts. Thus, we have been developing correction methods. Among them, we have recently improved correction methods for the non-linearity and the reset anomaly of the detector response. These corrections successfully reduce the artifact level down to $0.1MJy\;sr^{-1}$ on average, which is essential for discussion on faint extended emission (e.g., the Galactic PAH emission). We have also made progress in the subtraction of the scattered light caused in the camera optics. We plan to release the improved diffuse maps to the public within a year.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.39.2-39.2
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• 2020

Based upon the previous heritage in the complete development of the infrared imaging spectrometer, NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1, we are participating in the NASA MIDEX mission (PI Institute: Caltech), the all-sky infrared spectro-photometric surveyor SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer). The SPHEREx will provide us the first all-sky infrared spectro-photometric data set to probe the origin of our Universe, to explore the origin and evolution of galaxies, and to explore whether planets around other stars could harbor life. After the SPEHREx have passed the PDR (Preliminary Design Review) on this September, the fabrication of flight hardware will be started soon. As an international partner, KASI takes part in the hardware development, the operation and the science for the SPHEREx. Here, we report the status of the SPHEREx project and the progress in the Korean participation.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.367-373
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• 2012

The first all-sky mid-/far-infrared survey by IRAS in the 1980s, has been followed by only two more, by AKARI, from 2006, and WISE in 2010. I discuss some features of the WISE survey, and highlight some key results from early extragalactic observations that have been made by the science team during the operation of the telescope, and the post-operation proprietary period during which the public release data products were being generated. The efficient survey strategy and very high-data rate from WISE produced a catalogue of 530 million objects that was released to the public in March 2012. The WISE survey strategy naturally provided the deepest coverage at the ecliptic poles, where matched comparison fields were obtained using Spitzer, and where AKARI also observed deep fields. I describe some of the follow-up work that has been carried out based on the WISE survey, and the prospects for enhancing the WISE data by combining the AKARI survey results are also discussed. While the all-sky AKARI survey is less deep than the WISE catalogue, and is still being worked on by the AKARI science team, it includes a larger number of bands, extends to longer wavelengths, and in particular has very complementary band passes to WISE in the mid-infrared waveband, which will provide enhanced spectral information for relatively bright targets.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.62.1-62.1
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• 2019

Current large observational projects perform both static and dynamic sky surveys. The Thirty-Minute Target of Opportunity (TMT) is the project focusing on the dynamic sky survey using Korea Microlensing Telescope Network (KMTNet) that is the best observing system to investigate the dynamic sky. TMT aims to perform and experiment on following components : 1) to select transient or variable sources having hour to day scale cadences for future science cases, 2) to optimize the observation strategy for these objects, 3) to provide automated photometric pipelines for the time series data, and 4) to test the data release environment for all astronomers. In the near future, it is expected that a huge number of events will be alerted through large area surveys such as LSST. Therefore, the TMT project will provide opportunities to prepare the future large survey era as well as to understand the nature of interesting astronomical events.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.5-9
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• 2017

This paper provides an overview of the AKARI mission, which was the first Japanese satellite dedicated to infrared astronomy. The AKARI satellite was launched in 2006, and performed both an all-sky survey and pointed observations during its 550 days in the He-cooled mission phases (Phases 1 and 2). After the He ran out, we continued near-infrared observations with mechanical cryocoolers (Phase 3). Due to a failure of its power supply, AKARI was turned off in 2011. The AKARI data are unique in terms of the observed wavelengths as well as the sky coverage, and provide a unique legacy resource for many astronomical studies. Since April 2013, a dedicated new team has been working to refine the AKARI data processing. The goal of this activity is to provide processed datasets for most of the AKARI observations in a Science Ready form, so that more users can utilize the AKARI data in their astronomical research. The data to be released will include revised All-Sky Point Source Catalogues, All-Sky Image Maps, as well as high-sensitivity images and spectra obtained by pointed observations. We expect that the data will be made public by in the Spring of 2016.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.111-116
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• 2012

Far-infrared observations provide crucial data for the investigation and characterisation of the properties of dusty material in the Interstellar Medium (ISM), since most of its energy is emitted between ~ 100 and $200{\mu}m$. We present the first all-sky image from a sensitive all-sky survey using the Japanese AKARI satellite, in the wavelength range $50-180{\mu}m$. Covering > 99% of the sky in four photometric bands with four filters centred at $65{\mu}m$, $90{\mu}m$, $140{\mu}m$, and $160{\mu}m$ wavelengths, this achieved spatial resolutions from 1 to 2 arcmin and a detection limit of < 10 MJy $sr^{-1}$, with absolute and relative photometric accuracies of < 20%. All-sky images of the Galactic dust continuum emission enable astronomers to map the large-scale distribution of the diffuse ISM cirrus, to study its thermal dust temperature, emissivity and column density, and to measure the interaction of the Galactic radiation field and embedded objects with the surrounding ISM. In addition to the point source population of stars, protostars, star-forming regions, and galaxies, the high Galactic latitude sky is shown to be covered with a diffuse filamentary-web of dusty emission that traces the potential sites of high latitude star formation. We show that the temperature of dust particles in thermal equilibrium with the ambient interstellar radiation field can be estimated by using $90{\mu}m$, $140{\mu}m$, and $160{\mu}m$ data. The FIR AKARI full-sky maps provide a rich new data set within which astronomers can investigate the distribution of interstellar matter throughout our Galaxy, and beyond.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.347-352
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• 2012

Understanding infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and AGN evolution, since their most intense stages are often obscured by dust. Japanese infrared satellite, AKARI, provided unique data sets to probe this both at low and high redshifts. The AKARI performed an all sky survey in 6 IR bands (9, 18, 65, 90, 140, and $160{\mu}m$) with 3-10 times better sensitivity than IRAS, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can measure the total infrared luminosity ($L_{TIR}$) of individual galaxies much more precisely, and thus, the total infrared luminosity density of the local Universe. In the AKARI NEP deep field, we construct restframe $8{\mu}m$, $12{\mu}m$, and total infrared (TIR) luminosity functions (LFs) at 0.15 < z < 2.2 using 4,128 infrared sources. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and $24{\mu}m$) by the AKARI satellite allows us to estimate restframe $8{\mu}m$ and $12{\mu}m$ luminosities without using a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. By combining these two results, we reveal dust-hidden cosmic star formation history and AGN evolution from z = 0 to z = 2.2, all probed by the AKARI satellite.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.41.2-41.2
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• 2010

The infrared astronomy satellite AKARI/FIS (Far-Infrared Surveyor) performed all-sky survey in 4 Far-IR bands (50 - 200${\mu}m$ range). It observed around 94% of the whole sky twice or more with a higher spatial resolution and a wider wavelength coverage than that of previous all-sky mission, IRAS. The AKARI/FIS bright source catalogue ${\beta}-2$ is the second released version which included around 290,000 point sources. It provides us with more reliable position and flux information, and around 4 times larger number of sources compared with the first version of catalogue. The sensitivity limit at $90{\mu}m$ band is 0.6 Jy and the estimated flux uncertainty is 20-35% for bright sources. The catalogue will be open to public in this year after the improvement of accuracy, reliability and completeness.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.235-235
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• 2012

The "Widefield ASKAP L-band Legacy All-sky Blind surveY" (WALLABY) is an extragalactic HI survey which aims to examine HI properties and large-scale distribution of ~500,000 galaxies out to z ~ 0.27, covering a wide range of science goals associated with galaxy formation and evolution (P.I.: B. Koribalski & L. Staveley-Smith). The combination of ASKAP's exquisite column density sensitivity and a large primary beam will make it possible to systematically investigate the rarely explored low column-density HI in the universe. Ultimately, the largest and most homogeneous data set from WALLABY will drastically improve and broaden our knowledge on galaxy formation and evolution. ASKAP will be on-line in 2013, so to ensure timely and efficient reduction and analysis of the large WALLABY data set, we have been developing and testing reliable source finding tools and data analysis pipelines. In this talk I present recent progress of WALLABY, especially on the kinematic parameterisation pipeline for the spatially resolved galaxies detected by WALLABY.