• 천문학회보
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• 제36권2호
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• pp.126.1-126.1
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• 2011

The SPICA (SPace Infrared Telescope for Cosmology & Astrophysics) project is a next-generation infrared space telescope optimized for mid- and far-infrared observation with a cryogenically cooled 3m-class telescope. Owing to unique capability of focal plane instruments onboard SPICA, it will enable us to resolve many astronomical key issues from the star-formation history of the universe to the planetary formation. The FPC (Focal Plane Camera) is a Korean-led near-infrared instrument as an international collaboration. Korean consortium for FPC proposed a key instrument responsible for a fine guiding (FPC-G). The back-up of FPC-G will make scientific observations as well. We have examined the legacy science programs for FPC and performed the feasibility study for the fine guiding system. Recently, the international review process is now in progress, in order to make a selection of the focal plane instruments. Here, we report the current status of SPICA/FPC project.

• 천문학회지
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• 제49권5호
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• pp.225-232
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• 2016

We present an optical imaging survey of AKARI Deep Field South (ADF-S) using the Korea Microlensing Telescope Network (KMTNet), to find optical counterparts of dusty star-forming galaxies. The ADF-S is a deep far-infrared imaging survey region with AKARI covering around 12 deg², where the deep optical imaging data are not yet available. By utilizing the wide-field capability of the KMTNet telescopes (~4 deg²), we obtain optical images in B, R and I bands for three regions. The target depth of images in B, R and I bands is ~24 mag (AB) at 5σ, which enables us to detect most dusty star-forming galaxies discovered by AKARI in the ADF-S. Those optical datasets will be helpful to constrain optical spectral energy distributions as well as to identify rare types of dusty star-forming galaxies such as dust-obscured galaxy, sub-millimeter galaxy at high redshift.

• 문화기술의 융합
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• 제6권1호
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• pp.255-261
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• 2020

융복합적 인재란 자신의 전문 분야를 넘어서 다른 분야의 전문가들과 효율적인 협력 작업을 수행할 수 있는 인재를 의미하거나 아니면 스스로 다양한 분야의 지식을 융합해 낼 수 있는 인재를 의미한다. 이 논문에서는 역사적 인물들 중 다양한 분야의 지식을 융합해 내어 한 분야로의 지식만으로는 이룰 수 없는 성과를 도출해 냈던 사례로 갈릴레오를 살필 것이다. 논문에서는 르네상스 분위기 속에서 화가들과 교류했던 갈릴레오가 망원경으로 하늘을 관측한 결과를 그림으로 표현했다는 점과 그가 과거의 우주론을 비판하는 결정적인 논리를 만들어 내는 과정에서 그 그림들을 적극적으로 활용했음을 보일 것이다. 이러한 갈릴레오의 사례는 융합적 인재 양성에 있어서 목표로 삼아야 할 지향점을 제시해 준다는 점에 있어서 의미가 크다.

• 천문학회지
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• 제52권5호
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• pp.181-205
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• 2019

There is evidence that the luminosities of Type Ia supernova (SN Ia) depend on their environments. While the impact of this trend on estimating cosmological parameters is widely acknowledged, the origin of this correlation is still under debate. In order to explore this problem, we first construct the YONSEI (YOnsei Nearby Supernova Evolution Investigation) SN catalog. The catalog consists of 1231 spectroscopically confirmed SNe Ia over a wide redshift range (0.01 < z < 1.37) from various SN surveys and includes light-curve fit data from two independent light-curve fitters, SALT2 and MLCS2k2. For a sample of 674 host galaxies, we use the stellar mass and the star formation rate data in Kim et al. (2018). We find that SNe Ia in low-mass and star-forming host galaxies are $0.062{\pm}0.009mag$ and $0.057{\pm}0.010mag$ fainter than those in high-mass and passive hosts, after light-curve corrections with SALT2 and MLCS2k2, respectively. When only local environments of SNe Ia (e.g., locally star-forming and locally passive) are considered, this luminosity difference increases to $0.081{\pm}0.018mag$ for SALT2 and $0.072{\pm}0.018mag$ for MLCS2k2. Considering the significant difference in the mean stellar population age between the two environments, this result suggests that the luminosity evolution of SNe Ia with redshift is most likely the origin of the environmental dependence.

• 천문학회보
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• 제46권2호
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• pp.70.2-71
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• 2021

We examine gas kinematics and star formation activities of NGC 6822, a gas-rich dwarf irregular galaxy in the Local Group at a distance of ~490 kpc. We perform profile decomposition of all the line-of-sight (LOS) HI velocity profiles of the high-resolution (42.4" × 12" spatial; 1.6 km/s spectral) HI data cube of the galaxy, taken with the Australian Telescope Compact Array (ATCA). To this end, we use a novel tool based on Bayesian Markov Chain Monte Carlo (MCMC) techniques, the so-called BAYGAUD, which allows us to decompose a velocity profile into an optimal number of Gaussian components in a quantitative manner. We group all the decomposed components into bulk-narrow, bulk-broad, and non-bulk gas components classified with respect to their velocity dispersions and the amounts of velocity offset from the global kinematics, respectively. Using the surface densities and velocity dispersions of the kinematically decomposed HI gas maps together with the rotation curve of NGC 6822, we derive Toomre-Q parameters for individual regions of the galaxy which quantify the level of local gravitational instability of the gaseous disk. We also measure the local star formation rate (SFR) of the corresponding regions in the galaxy by combining GALEX Far-ultraviolet (FUV) and WISE 22㎛ images. We then relate the gas and SFR surface densities in order to investigate the local Kennicutt-Schmidt (K-S) law of gravitationally unstable regions which are selected from the Toomre Q analysis. Of the three groups, the bulk-narrow, bulk-broad and non-bulk gas components, we find that the lower Toomre-Q values the bulk-narrow gas components have, the more consistent with the linear extension of the K-S law derived from molecular hydrogen (H2) observations.

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.377-384
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• 2005

감마선 폭발체는 1973년 처음으로 알려진 후 현재까지 많은 과학자들에 의해 연구되고 있다. 짝은 지속 기간을 가진 감마선 폭발체에 비해 비교적 긴 시간 척도를 가진 잔유휘광의 분광 분석자료는 감마선 폭발체 생성 환경 연구에 중요한 정보를 제공한다. 그러나, 모든 감마선 폭발체에서 모든 영역의 잔유휘광이 관측되는 것은 아니다. 전파나 엑스선 영역의 잔유휘광 관측 불능은 검출기나 광대역 모니터의 한계로 인한 문제로 보고 있으며, 광학 잔유휘광 관측 불능은 광원내부 또는 소속 은하내의 먼지 그리고 성간 매질의 흡수에 의한 것으로 보고 있다. 우리는 이러한 잔유휘광이 관측되지 않은 경우에 대해 의문을 가지고, 광학 관측으로 거리가 정해진 감마선 폭발체의 거리에 따른 에너지 영역별 잔유휘광 개수 분포를 비교 분석해 보았다. 그 결과 우리는 엑스선 잔유휘광이 관측된 감마선 폭발체들이나 광학 잔유휘광이 관측된 감마선 폭발체들의 거리 분포가 같다는 것을 알 수 있었다. 이같은 결과로부터 우리는 광학 잔유휘광이 성간 물질에 의한 소광으로 관측되지 않을 수 있다는 이론은 타당치 못하다는 결론을 주장해 본다.

• 천문학회보
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• 제38권1호
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• pp.36.2-36.2
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• 2013

The SPICA (SPace Infrared Telescope for Cosmology & Astrophysics) project is a next-generation infrared space telescope optimized for mid- and far-infrared observation with a cryogenically cooled 3m-class telescope. The focal plane instruments onboard SPICA will enable us to resolve many astronomical key issues from the formation and evolution of galaxies to the planetary formation. The FPC-S (Focal Plane Camera - Sciecne) is a near-infrared instrument proposed by Korea as an international collaboration. Owing to the capability of both low-resolution imaging spectroscopy and wide-band imaging with a field of view of $5^{\prime}{\times}5^{\prime}$, it has large throughput as well as high sensitivity for diffuse light compared with JWST. In order to strengthen advantages of the FPC-S, we propose the studies of probing population III stars by the measurement of cosmic near-infrared background radiation and the star formation history at high redshift by the discoveries of active star-forming galaxies. In addition to the major scientific targets, to survey large area opens a new parameter space to investigate the deep Universe. The good survey capability in the parallel imaging mode allows us to study the rare, bright objects such as quasars, bright star-forming galaxies in the early Universe as a way to understand the formation of the first objects in the Universe, and ultra-cool brown dwarfs. Observations in the warm mission will give us a unique chance to detect high-z supernovae, ices in young stellar objects (YSOs) even with low mass, the $3.3{\mu}$ feature of shocked circumstance in supernova remnants. Here, we report the current status of SPICA/FPC project and its extragalactic sciences.

• 천문학회지
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• 제47권2호
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• pp.77-86
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• 2014

Using a cosmological ${\Lambda}CDM$ simulation, we analyze the differences between the widely-used spin parameters suggested by Peebles and Bullock. The dimensionless spin parameter ${\lambda}$ proposed by Peebles is theoretically well-justified but includes an annoying term, the potential energy, which cannot be directly obtained from observations and is computationally expensive to calculate in numerical simulations. The Bullock's spin parameter ${\lambda}^{\prime}$ avoids this problem assuming the isothermal density profile of a virialized halo in the Newtonian potential model. However, we find that there exists a substantial discrepancy between ${\lambda}$ and ${\lambda}^{\prime}$ depending on the adopted potential model (Newtonian or Plummer) to calculate the halo total energy and that their redshift evolutions differ to each other significantly. Therefore, we introduce a new spin parameter, ${\lambda}^{\prime\prime}$, which is simply designed to roughly recover the value of ${\lambda}$ but to use the same halo quantities as used in ${\lambda}^{\prime}$. If the Plummer potential is adopted, the ${\lambda}^{\prime\prime}$ is related to the Bullock's definition as ${\lambda}^{\prime\prime}=0.80{\times}(1+z)^{-1/12}{\lambda}^{\prime}$. Hence, the new spin parameter ${\lambda}^{\prime\prime}$ distribution becomes consistent with a log-normal distribution frequently seen for the ${\lambda}^{\prime}$ while its mean value is much closer to that of ${\lambda}$. On the other hand, in case of the Newtonian potential model, we obtain the relation of ${\lambda}^{\prime\prime}=(1+z)^{-1/8}{\lambda}^{\prime}$; there is no significant difference at z = 0 as found by others but ${\lambda}^{\prime}$ becomes more overestimated than ${\lambda}$ or ${\lambda}^{\prime\prime}$ at higher redshifts. We also investigate the dependence of halo spin parameters on halo mass and redshift. We clearly show that although the ${\lambda}^{\prime}$ for small-mass halos with $M_h$ < $2{\times}10^{12}M_{\odot}$ seems redshift independent after z = 1, all the spin parameters explored, on the whole, show a stronger correlation with the increasing halo mass at higher redshifts.