• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.55.2-55.2
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• 2015

NISS is a unique spaceborne imaging spectrometer (R = 20) onboard the Korea's next micro-satellite NEXTSat-1 to investigate the star formation history of Universe in near infrared wavelength region (0.9 - 3.8 um), with a customized H1RG IR sensor(Jeong 2014). In this paper, we will introduce the compact electronics system (Fig. 1) as well as the novel readout method to reduce the 1/f noise for NISS.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.447-449
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• 2015

Although the link between activity in the nuclei of galaxy and galactic mergers has been under scrutiny for several years, it is still unclear to what extent and for which populations of active galaxies merger-triggered activity is relevant. The environments of AGN allow an indirect probe of the past merger history and future merger probability of these systems, suffering less from sensitivity issues when extended to higher redshifts than traditional morphological studies of AGN host galaxies. Here we present results from our investigation of the environment of radio selected sources out to a redshift z=2. We employ the first data release J-band catalog of the new near-IR Infrared Medium-Deep Survey (IMS), 1.4 GHz radio data from the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey and a deep dedicated VLA survey of the VIMOS field, covering a combined total of 20 sq. degrees. At a flux limit of the combined radio catalog of 0.1 mJy, we probe over 8 orders of magnitude of radio luminosity. Using the second closest neighbor density parameters, we test whether active galaxies inhabit denser environments. We find evidence for a sub-population of radio-selected AGN that reside in significantly overdense environments at small scales, although we do not find significant overdensities for the bulk of our sample. We show that radio-AGN in the most underdense environments have vigorous ongoing star formation. We interpret these results in terms of the triggering and fuelling mechanism of radio-AGN.

• Journal of The Korean Astronomical Society
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• v.52 no.5
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• pp.159-172
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• 2019

It is known that the number of astronomers of a country registered to the International Astronomical Union (IAU) is correlated with that country's gross domestic product (GDP). However, the robustness of this relationship could be doubted, as the fraction of astronomers joining the IAU differs from country to country. Here we revisit this correlation by using more recent data, updated as of 2017. We find a similar correlation by using the total number of astronomers and astrophysicists with PhD degrees that are working in each country, instead of adopting the number of IAU members. We confirm the existence of the correlation. We also confirm the existence of two subgroups within this correlation. One group consists of advanced European countries having a long history of modern astronomy, while the other group consists of countries having experienced recent rapid economic development. In order to determine the cause for the correlation, we obtained the long-term variations of the number of astronomers, population, and the GDP for a number of countries. We find that the number of astronomers per capita for recently developing countries has increased more rapidly as GDP per capita increased, than that for fully developed countries. We collected demographic data of the Korean astronomical community and find that it has experienced recent rapid growth. From these findings we estimate the proper size of the Korean astronomical community by considering Korea economic power and population. The current number of PhD astronomers working in Korea is approximately 310, but it should be 550 in order for it to be comparable and competitive to the sizes of the Spanish, Canadian, and Japanese astronomical communities. If current trends continue, this number will be reached by 2030. In order to be comparable to the German, French, and Italian communities, there should be 800 PhD astronomers in Korea. We discuss ways to overcome the vulnerability of the Korean astronomical community, based on the statistics of national R&D expenditure structure in comparison with that of other major advanced countries.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.213-217
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• 2017

The recent updates of the North Ecliptic Pole deep ($0.5deg^2$, NEP-Deep) multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of $15{\mu}m$ or $18{\mu}m$ selected galaxies, which is the largest sample ever made at these wavelengths. A continuous filter coverage in the mid-infrared wavelength (7, 9, 11, 15, 18, and 24 µm) is unique and vital to diagnose the contributions from starbursts and AGNs in the galaxies out to z=2. The new goal of the project is to resolve the nature of the cosmic star formation history at the violent epoch (e.g. z=1-2), and to find a clue to understand its decline from z=1 to present universe by utilizing the unique power of the multiwavelength survey. The progress in this context is briefly mentioned.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.67-72
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• 2014

The next generation small satellite-1 (NEXTSat-1) program has been kicked off in 2012, and it will be launched in 2016 for the science missions and the verification of space core technologies. The payloads for these science missions are the Instrument for the Study of Space Storms (ISSS) and NIR Imaging Spectrometer for Star formation history (NISS). The ISSS and the NISS have been developed by Korea Advanced Institute of Science and Technology (KAIST) and Korea Astronomy and Space science Institute (KASI) respectively. The ISSS detects plasma densities and particle fluxes of 10 MeV energy range near the Earth and the NISS uses spectrometer. In order to verify the spacecraft core technologies in the space, the total of 7 space core technologies (SCT) will be applied to the NEXTSat-1 for space verification and those are under development. Thus, the operation modes for the ISSS and the NISS for space science missions and 7 SCTs for technology missions are analyzed for the required operation time during the NEXTSat-1's mission life time of 2 years. In this paper, the operational concept of the NEXTSat-1's science missions as well as the verification of space core technologies are presented considering constraints of volume, mass, and power after launch.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.45.1-45.1
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• 2013

Type Ia supernovae (SNe Ia) are a powerful tool to investigate the expansion history of the universe, because their peak luminosity is as bright as a galaxy and is known as an excellent standard candle. Since the discovery of the acceleration of the universe based on the observations of SNe Ia, higher than ever accuracy of their peak luminosity is needed to investigate various problems in cosmology. We started a project to improve the accuracy of the calibration of the peak luminosity of SNe Ia by measuring accurate distances to nearby resolved galaxies that host SNe Ia. We derive accurate distances to the SN Ia host galaxies using the method to measure the luminosity of the tip of the red giant branch (TRGB). In this study we present the results for M66 and M96 in the Leo I Group which are nearby spiral galaxies hosting SN 1989B and SN 1998bu, respectively. We obtain VI photometry of resolved stars in these galaxies from F555W and F814W images in the Hubble Space Telescope archive. We derive the distances to these galaxies from the luminosity of the TRGB. With these results we derive absolute maximum magnitudes of two SNe (SN 1989B in M66 and SN 1998bu in M96). We derive a value of the Hubble constant from the optical magnitudes of these SNe Ia and SN 2011fe in M101 based on our TRGB analysis. This value is similar to the values derived from recent estimates from WMAP9 and Planck results, but smaller than other recent determinations based on Cepheid calibration for SNe Ia luminosity.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.50.4-51
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• 2015

대덕 14m 전파망원경에 의한 밀리미터파 관측연구 경험을 바탕으로 시작된 한국우주전파관측망 (Korean VLBI Network: KVN) 사업은 2001년 예산이 확보됨으로써 본격화되기 시작하였다. 현재는 짧은 밀리미터파 대역을 포함한 22/43/86/129 GHz 대역의 세계 최초 4밴드 동시관측 시스템으로서 국제적 주목을 받으며 국내는 물론 일본 중국 대만의 동아시아지역 공동활용과 세계적 오픈도 눈앞에 두며 그 핵심과학연구에 진입하는 단계에 와있다. 여기에서는 그 동안의 KVN 건설, 수신시스템, 한일 상관기 및 공동네트워크 구축, 연구관측에 이르기까지 걸어온 길과 앞으로의 방향을 조명해 본다.

• Journal for History of Mathematics
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• v.32 no.6
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• pp.259-270
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• 2019

Haidao Suanjing was introduced into Joseon by discussion in Yang Hui Suanfa (楊輝算法) which was brought into Joseon in the 15th century. As is well known, the basic mathematical structure of Haidao Suanjing is perfectly illustrated in Yang Hui Suanfa. Since the 17th century, Chinese mathematicians understood the haidao problem by the Western mathematics, namely an application of similar triangles. The purpose of our paper is to investigate the history of the haidao problem in the Joseon Dynasty. The Joseon mathematicians mainly conformed to Yang Hui's verifications. As a result of the influx of the Western mathematics of the Qing dynasty for the study of astronomy in the 18th century Joseon, Joseon mathematicians also accepted the Western approach to the problem along with Yang Hui Suanfa.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.40.1-40.1
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• 2019

We utilize times since infall of cluster galaxies obtained from Yonsei Zoom-in Cluster Simulation (YZiCS), the cosmological hydrodynamic N-body simulations, and star formation rates from the SDSS data release 10 to study how quickly late-type galaxies are quenched in the cluster environments. In particular, we confirm that the distributions of both simulated and observed galaxies in phase-space diagrams are comparable and that each location of phase-space can provide the information of times since infall and star formation rates of cluster galaxies. Then, by limiting the location of phase-space of simulated and observed galaxies, we associate their star formation rates at z ~ 0.08 with times since infall using an abundance matching technique that employs the 10 quantiles of each probability distribution. Using a flexible quenching model covering different quenching scenarios, we find the star formation history of satellite galaxies that best reproduces the obtained relationship between time since infall and star formation rate at z ~ 0.08. Based on the derived star formation history, we constrain the quenching timescale (2 - 7 Gyr) with a clear stellar mass trend and confirm that the refined model is consistent with the "delayed-then-rapid" quenching scenario: the constant delayed phase as ~ 2.3 Gyr and the quenching efficiencies (i.e., e-folding timescale) outside and inside clusters as ~ 2 - 4 Gyr (${\propto}M_*^{-1}$) and 0.5 - 1.5 Gyr (${\propto}M_*^{-2}$), Finally, we suggest: (i) ram-pressure is the main driver of quenching of satellite galaxies for the local Universe, (ii) the quenching trend on stellar mass at z > 0.5 indicates other quenching mechanisms as the main driver.

• Cross-Cultural Studies
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• v.25
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• pp.597-626
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• 2011

Civil college is a public educational institute for theoretical and practical learning. This study examines the social context behind France's civil college and how it is being operated. Many studies have been conducted in Korea to examine Germany in terms of lifelong learning or adult learning, but there is almost no study on France. Therefore, this study was conducted to analyze the history and operation of civil college, the "college outside college," in France and what Korea should learn from it. The civil college of France can be discussed in two contexts: first, it is AUPF, which stands for the French association of civil colleges, and it was mostly influenced by Northern Europe and Germany. Second, it is Caen Civil College, which was established by M. Onfray based his philosophical collaboration. The European civil college opened almost 1,000 courses in 2010-2011 for a variety of subjects, including Foreign Languages, Mother Tongue, the Dialects of Alsace, Philosophy, Cosmology, History, Art History, Psychology, Sociology, Astronomy, Botany, and Natural Science. Courses in Fine Arts include drawing, painting, sculpture, photography, music, and theater. For another form of civil college, Philosopher M. Onfray has been operating Caen Civil College since 2002 for general education and cultural education. It is not acknowledged by conventional philosophers, but it is contributing to the popularization of philosophy. In conclusion, the civil college in France has brought in-depth philosophical discussions out of the lecture rooms in an effort to popularize learning, making lifelong learning more accessible to the general public.