• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.54.3-54.3
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• 2015

To probe the star formation in local and early Universe, the NISS with a capability of imaging spectroscopy in the near-infrared is being developed by KASI. The main scientific targets are nearby galaxies, galaxy clusters, star-forming regions and low background regions. The off-axis optical design of the NISS with 15cm aperture was optimized to obtain a wide field of view (FoV) of $2deg.{\times}2deg.$ as well as a wide spectral coverage from 0.9 to $3.8{\mu}m$. The opto-mechanical structure was designed to be safe enough to endure in both the launching condition and the space environment. The dewar will operate $1k{\times}1k$ infrared sensor at 80K stage. The NISS will be launched in 2017 and explore the large areal near-infrared sky up to $200deg.^2$ in order to get both spatial and spectral information for astronomical objects. As an extension of the NISS, KASI is planning to participate in a new small space mission together with NASA. The promising candidate, SPHEREx (Spectro-Photometer for the History of the Universe Epoch of Reionization, and Ices Explorer) is an all-sky survey satellite designed to reveal the origin of the Universe and water in the planetary systems and to explore the evolution of galaxies. Though the survey concept is similar to that of the NISS, the SPHEREx will perform the first near-infrared all-sky imaging spectroscopic survey with the wider spectral range from 0.7 to $5{\mu}m$ and the wider FoV of $3.5deg.{\times}7deg.$ Here, we report the current status of the NISS and introduce new mission for the near-infrared imaging spectroscopic survey.

• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.239-259
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• 2022

Since 2019, research on microplastics has been actively conducted around the world, so analyzing the differences between domestic and foreign microplastics research can be a milestone in establishing the direction of domestic research. In this study, microplastic papers from KCI and WoS were extracted and the differences between domestic and foreign studies were analyzed using a network analysis methodology based on big data such as author keyword co-occurrence word analysis, thesis co-citation analysis, and author co-citation analysis. As a result of the analysis, the analysis of the research topic confirmed that studies that could affect the human body and the treatment of microplastics in daily life were additionally needed in Korea. In the analysis of the depth of thesis citation that examines the quality of research, it was found that Korea was still insufficient at 2.25 overseas and 1.39 in Korea. In the analysis of the composition of the joint research front, where various researchers participate and share information, 3 out of 22 clusters in Korea are Star type. In the case of overseas, all 19 clusters have a mesh structure, so it was confirmed that information flow and sharing were insufficient in specific research fields in Korea. These research results confirmed the need to expand the research topic of microplastics, improve the quality of research, and improve the research promotion system in which various researchers participate. In addition, if the automation program is developed based on topic modeling, it will be possible to build a system capable of real-time analysis.

• Journal of The Korean Astronomical Society
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• v.41 no.5
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• pp.121-137
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• 2008

We present optical and near-infrared imaging and long-slit spectroscopy for the blue compact dwarf galaxy (BCD) Mrk 49 in the Virgo Cluster. The surface brightness distribution analysis shows that Mrk 49 consists of an off-centered blue bright compact core of r = 10" and a red faint outer exponential envelope. The $H_{\alpha}$ image and color difference suggest that these two components have different stellar populations: a high surface brightness population of massive young stars and an underlying low surface brightness population of older stars. The redder near-infrared colors of the inner most region suggest that the near-infrared flux of Mrk 49 originates from evolved massive stars associated with the current star-forming activity. The total apparent magnitude is $B_T\;=\;14.32$ mag and the mean effective surface brightness is ${\mu}_{eff}(B)\;=\;21.56$ mag $arcsec^{-2}$. Long-slit spectroscopy shows that Mrk 49 rotates apparently as a solid body within r = 10" in a plane at position angle 55 degrees with an amplitude of about $20\;km\;sec^{-1}$. The measured radial velocity of Mrk 49 was derived as $1,535\;km\;sec^{-1}$; and the total mass of stars and gases is in the range of 3 to $6\;{\times}\;10^9\;M_{\odot}$. The mass-to-light ratios for the central region of Mrk 49 in I and B band are estimated 1.0 and 0.5, respectively. The upper limit of the dark matter to visible matter ratio seems to be < 5. The oxygen abundance is $12\;+\;\log(O/H)\;=\;8.21\;{\pm}\; 0.1$ which is about one quarter of the solar value while the relative helium abundance appears to be similar to that of the sun.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.39.4-40
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• 2016

We aim to investigate formation of satellite sub-galactic structures around isolated dwarf galaxies using cosmological hydrodynamic zoom simulations. For this, we modify a cosmological hydrodynamic code, GADGET-3, in a way that includes gas cooling down to T~10K, gas heating by universal reionization when z < 8.9, UV shielding for high density regions of $n_{shield}$ > $0.014cm^{-3}$, star formation in the dense regions ($n_H$ > $100cm^{-3}$), and supernova feedback. To get good statistics, we perform three different simulations for different target galaxies of the same mass of ${\sim}10^{10}M_{sun}$. Each simulation starts in a cubic box of a side length of 1Mpc/h with 17 million particles from z = 49. The mass of dark matter (DM) and gas particle is $M_{DM}=4.1{\times}10^3M_{sun}$ and $M_{gas}=7.9{\times}10^2M_{sun}$, respectively, thus each satellite sub-galactic structure can be resolved with more than hundreds or thousands particles. We analyze total 90 sub-galactic structures that have formed outside of the main halos but infall the main halos. We found that 1) mini halos that interact more with the other mini halos tend to accrete the more mass, 2) mini halos that interact more before the reionization tend to form more stars, 3) mini halos with the more interaction tend to approach closer to the galactic center and have the lower orbital circularity, 4) survivals even in the strong tidal fields evolve baryon dominated system, such as globular clusters.

• Journal of the Korea Computer Graphics Society
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• v.29 no.3
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• pp.105-115
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• 2023

In this paper, we describe the process and method of converting tens of TB of time-varying AMR (adaptive mesh refinement) volume data generated as a result of numerical model simulation into optimized data that can be used for various XR devices. AMR volume data is a useful data format for complex modeling and simulation, and it can efficiently express materials such as star clusters and gases that exist in the very wide outer space used in this study. we analyzes the metadata of AMR data, samples it at low resolution, optimizes information in important areas, and converts it into a data set that can be used even on relatively low performance XR devices. Finally, we introduces how the optimized data was utilized and visualized through the development of immersive XR content using the data set.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.249-262
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• 2004

The variations of the dynamical substructures of NGC 6934 have been investigated by means of performing point spread function stellar photometry and the surface photometry on BV CCD images of NGC 6934. Our results show that overall variations of ellipticity and position angle range in $0.02{\sim}0.08\;and\;-90^{\circ}{\sim}+90^{\circ}$, respectively out to three times the half light radius. The inner ($r_{eff}) substructures of NGC 6934 inferred from the variations of ellipticity and position angle are mainly affected by the bright red giant populations, while the effects of the other giant populations are weaker than those of the bright red giant populations. Horizontal branch populations and faint red giant star populations affect the dynamical substructures of NGC 6934 in the region of $r_h.

• Publications of The Korean Astronomical Society
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• v.27 no.5
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• pp.399-409
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• 2012

As a part of the short-period variability survey (SPVS) at Bohyunsan Optical Astronomy Observatory, we obtained time-series BV CCD images in the region of Cyg OB3 association centered on the open cluster NGC 6871. The observations were performed for 18 nights from September 5, 2008 to September 1, 2009. We found 15 short-period variable stars in the region. They are ${\delta}$ Scuti type stars belonging to the local spiral arm, Orion spur. Among them, only two stars were previously known, and the rest are newly discovered ones. In this paper, we have performed a multiple-frequency analysis to determine frequencies of the 15 ${\delta}$ Scuti type stars, using the discrete Fourier transform and linear least-square fitting methods. One of the newly discovered variable stars is a double-mode ${\delta}$ Scuti type star with the fundamental and the first overtone modes, and two are high amplitude ${\delta}$ Scuti stars.