• 천문학회보
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• 제42권2호
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• pp.59.4-59.4
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• 2017

We present a way of quantitatively characterizing solar active regions on the basis of their evolutionary paths. To determine characteristic properties of active regions with different sizes and configurations, we use a physics-based model to derive a relation between emerged magnetic flux and injected magnetic helicity (Flux-Helicity relation), the former of which gives scale information while the latter represents the magnetic field configuration of an active region. We demonstrate how this relation provides evolutionary paths of active regions and determines their characteristic properties, through a comparison with modeled active regions obtained from magnetohydrodynamic simulations.

• 천문학회보
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• 제43권1호
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• pp.47.2-47.2
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• 2018

In this talk, we will review extragalactic science cases with NISS and SPHEREx. With its capability to perform a low resolution spectroscopy over a wide area, NISS and SPHEREx can provide valuable information about the evolution of spectral shapes of galaxies in different environments over cosmic history. This talk will focus on the cases for the studies that are closely related to the galaxy evolution and formation.

• 천문학회지
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• 제31권2호
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• pp.89-93
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• 1998

An attempt is made to find the boundary tangential components of potential magnetic fields without constructing solutions in the entire domain. In our procedure, the magnetic energy is expressed as a functional of tangential and normal magnetic fields at the boundary and is minimized by the variational principle. This paper reports a preliminary study on two dimensional potential fields above a plane.

• 천문학회보
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• 제41권1호
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• pp.56.3-56.3
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• 2016

북한의 과학기술은 전반 수준이 낮은 것으로 평가 받고 있으나 국방 및 기초과학 영역에서는 높게 평가받는 부분도 있다. 북한 정권의 과학기술 중시 사상에 따라 과학기술자의 우대 정책은 현 김정은 시대에 더 강조되고 있다. 북한의 과학기술은 현장 중심으로 진행되는 게 큰 특징이다. 식량과 에너지 문제 해소를 위한 과학기술자의 현장동원 등과 함께, 이른바 강성국가 건설의 경제발전 핵심전략으로 '최신 과학기술에 기초한 현대화 실현'을 강조하고 있다. 북한의 과학원통보 등 학술지와 국제 학술논문 그리고 발명 특허, 북한의 언론매체 등을 통해 북한의 과학기술에 대한 전반적인 활동 상황과 최근의 흐름을 살펴본다.

• 천문학회보
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• 제39권1호
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• pp.31-31
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• 2014

I provide an observer's view on the recent BICEP2 results. I begin with giving background information on the instrument and CMB polarization measurements. Based on a survey of the current debate, I will provide an overview on the conclusions to be drawn from the BICEP2 measurements which are actually mixed: on the hand, there is no doubt that the results are very important and exciting; on the other hand, it is probably premature to conclude that the observed signal is indeed cosmological.

• 천문학회보
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• 제36권1호
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• pp.46.2-46.2
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• 2011

Planck is already in active operation, and in a few years a detailed CMB anisotropy map will be compiled, surpassing WMAP both in temperature and polarization. The E mode - E mode autocorrelation power spectrum at large scales contains weak but sizable information on the history of cosmic reionization. We show our latest advance of our own simulation of cosmic reionization that incorporates Pop III stars, and provide a forecast for Planck polarization measurement.

• 천문학회보
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• 제45권1호
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• pp.57.3-57.3
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• 2020

The chemical and kinematic properties of stars in the Galactic halo provide crucial information on the origin of the Galactic halo as well as the assembly history of the Milky Way. In this study, we present metallicity distribution functions (MDFs) in different regions of the Galactic halo as well as the kinematic characteristics in each region. The different MDFs and kinematic properties of stars in investigated regions allow us to associate them with the possible progenitor dwarf galaxies discovered to date; hence the assembly history of the Galactic halo.

• 천문학회보
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• 제40권2호
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• pp.50.4-51
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• 2015

Current and planned deep multicolor wide-area cosmological surveys will map in detail the spatial distribution of galaxies and quasars over unprecedented volumes, and provide a number of objects with photometric redshifts more than an order of magnitude bigger than that of spectroscopic redshifts. Photometric information is statistically more significant for studying cosmological evolution, dark energy, and the expansion history of the universe at a fraction of the cost of a full spectroscopic survey, but intrinsically carries a bias due to noise in the distance estimates. We provide convolution- and deconvolution-based algorithms capable of removing this bias -- thus able to exploit the full cosmological information -- in order to reconstruct intrinsic distributions and correlations between distance-dependent quantities. We then show some direct applications of our techniques to the VIMOS Public Extragalactic Redshift Survey (VIPERS) and the Sloan Digital Sky Survey (SDSS) datasets. Our methods impact a broader range of studies, when at least one distance-dependent quantity is involved; hence, they will be useful for upcoming large-volume surveys, some of which will only have photometric information.

• 천문학논총
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• 제30권2호
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• pp.719-720
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• 2015

These days, advanced technologies provide an easy way for the public to obtain information about anything, including astronomy. Most people know astronomy for its sky events and scientific results. In Indonesia, the public has a high interest not only in astronomy information but also in participating in astronomy events, but it is limited to those who has access to a club nearby. Otherwise, for those who live in remote areas or simply don't have any access, they depend on information from newspapers, magazines, books or word of mouth. They usually think that astronomy is a difficult subject to learn, while in fact it is something doable and fun.

• 천문학회보
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• 제40권2호
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• pp.31.1-31.1
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• 2015

For probing magnetic fields in the universe, rotation measure (RM) have been often used. RM allows us to obtain the information of integrated (or averaged) magnetic fields along a line of sight (LOS). On the other hand, the new technique so-called Faraday tomography will be used in practical in the near future thanks to the wide-band polarimetry by Square kilometre Array and/or its precursors. The technique allows us to obtain so-called Faraday dispersion function (FDF). FDF is the distribution function of magnetic fields and polarized sources along a LOS. Because of this fact, it is expected that the studies of magnetic fields associated with various astronomical objects will progress dramatically. Since FDF also includes information of cosmic-rays and thermal electrons, the investigation of FDF may advance the studies of dynamics of external galaxies and/or the star formation activities. We have studied the potentials of Faraday tomography such as a tool to probe the intergalactic magnetic field associated with filaments of galaxies in the large scale structure. We have also studied the realistic FDFs of galaxies for understanding global magnetic field, cosmic-ray and thermal electrons of external galaxies. In the talk, we briefly introduce the Faraday tomography technique and report the results related to the Faraday tomography.