• 천문학회보
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• 제46권2호
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• pp.56.3-56.3
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• 2021

In a ΛCDM universe, most galaxies are believed to evolve by mergers and accretions. The debris resulting from such processes remains faint and/or diffuse structures, such as tidal streams and stellar halos. Although these structures are a good indicator of the recent mass assembly history of galaxies, they have the disadvantage of being difficult to observe due to their low surface brightness (LSB). To recover these LSB features by reducing the photometric uncertainties introduced by the optics system, we attempt to develop an optimized telescope, called a linear astigmatism free-three mirror system, that minimizes the loss and scattering of light within the telescope. With that prototype, we observe NGC 5907, known as a nearby galaxy with a fabulous loop structure(s), to inspect its performance. After a dedicated data reduction process, including flat-fielding with dark sky flat and sky subtraction, our observation reaches a 1σ surface brightness limit of μlim,r ≃ 28.3 mag arcsec-2 in 10×10 arcsec boxes. We finally identify a single tidal stream that is likely the remnant of a nearly disrupted galaxy. This finding emphasizes that the capability of LSB detection with our telescope is comparable to that of much larger telescopes.

• 천문학회보
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• 제38권2호
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• pp.45.2-45.2
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• 2013

We studied recent evolution of M31 and M33 with star-forming regions and hot massive stars. We use GALEX far-UV and near-UV imaging to detect the star-forming regions and trace the recent star formation across the entire disk of galaxies. The GALEX imaging, combining deep sensitivity and entire coverage of these galaxies, provides a complete picture of the recent star formation in M31 and M33, and its variation with environment throughout these galaxies. We also show results from recent extensive surveys in M31 and M33 with Hubble Space Telescope multi-wavelength data including UV filters, which imaged several regions at a linear resolution of less than half a pc in these galaxies. Both datasets allow us to study the hierarchical structure of star formation: the youngest stellar groups are the most compact, and are often arranged withing broader, sparser structures. The derived recent star-formation rates are rather similar for the two galaxies, when scaled for the respective areas.

• 천문학회지
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• 제38권2호
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• pp.135-140
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• 2005

This paper summarizes the recent progress made by our group at Seoul National University on studies of the evolution and formation of distant galaxies. Various research projects are currently underway, which include: (i) the number density of distant early-type galaxies (z < 1); (ii) the optical-NIR color gradient of nearby early-type galaxies; (iii) J - K-selected Extremely Red Objects (EROs) in field (CDF-S) and the cluster environment; and (iv) the Lyman-break galaxies in the Spitzer First Look Survey (FLS) field. These works will constrain the mass evolution and the star formation history of galaxies in different environments, and the results will serve as useful contraints on galaxy formation models.

• 천문학회보
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• 제42권2호
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• pp.65.5-66
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• 2017

In the history of astronomy, observed data were interpreted very frequently based upon data measured at laboratories. For example, all the spectroscopic observations were understood via spectroscopic measurements on nuclei, atoms, and molecules. Recently, computational astrophysics plays a role of bridging experimental data to observations, in particular via numerical modeling of complex astronomical phenomena. This presentation focuses on computational nuclear astrophysics that connects experimental data on nuclei to high-energy observation data obtained by X-ray and gamma-ray telescopes. As an example case, X-ray burst will be discussed. In this phenomenon, observed X-ray light curves and spectra can be modeled by stellar evolution calculations that take nuclear reactions of rare isotopes as input information. This presentation also works as an introduction to the following presentation that will provide more detailed discussion on the experimental aspect of X-ray burst.

• 천문학회보
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• 제43권2호
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• pp.49.1-49.1
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• 2018

The Xinfa Suanshu, which was an important astronomical book in East-Asia, was published in 1644. This book was including the star catalogue. We researched the data of 1365 stars recorded in this star catalogue (the equinox of the catalogue is identified to be 1628 year). According to our analysis, it can be presumed that the star catalogue's data were observed from at least two places or more. Based on historical background, we assumed that the Xinfa Sunashu's catalogue likely referenced knowledge from the Europe or Arab/Islamic culture. The researchers who have studied the Xinfa Sunashu's star catalogue have all focused on Brahe's star catalogue. But they did not provide clear evidence. Therefore, we are compared with the star data recorded in Tablae Rudolphinae. In conclusion, we confirmed that 881 stars among the 1365 stars were perfectly edited from position data of stars recorded in Brahe's star catalogue (1602).

• 천문학회보
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• 제44권2호
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• pp.53.1-53.1
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• 2019

The cosmic dark sector, composed of dark energy and dark matter, might be coupled, and hence mediate a fifth-force which gives rise to distinctive cosmological signatures. I will consider an interacting dark sector, in which dark energy and dark matter are coupled via specific well-motivated coupling functions. After an overview of these coupled dark energy models, I will discuss the current model parameter constraints derived from the latest cosmological observations which probe the expansion history, and the growth of cosmic structures of our Universe. Moreover, I will demonstrate how different measurements of the Hubble constant, including the GW170817 measurement, influence the inferred constraints on the dark coupling. I will further discuss how one could put tighter constraints on such a dark sector coupling with the upcoming large-scale radio surveys.

• 천문학회보
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• 제44권2호
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• pp.61.2-61.2
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• 2019

The 『Hun-Gai-Tong-Xian-Tushuo 渾蓋通憲圖說』, which was an important astronomical book in East-Asia, was published by Li Zhi-zao (李之藻, 1565-1631) in 1607. This book was including the data of stars. We analyzed the data of stars recorded in 『Hun-Gai-Tong-Xian-Tushuo 渾蓋通憲圖說』. Based on historical background, we assumed that the data of stars recorded in 『Hun-Gai-Tong-Xian-Tushuo 渾蓋通憲圖說』 likely referenced knowledge from the ancient Arab/Islam culture. In conclusion, we assume a correlation with the star catalogue included in 『Almagest』 by Ptolemaios. Therefore, we think that this star's data will become important data for comparison with the star catalogues published in Arabic/Islam.

• 천문학회지
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• 제40권4호
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• pp.83-89
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• 2007

A new type of object called "Very Low Luminosity Objects (VeLLOs)" has been discovered by the Spitzer Space Telescope. VeLLOs might be substellar objects forming by accretion. However, some VeLLOs are associated with strong outflows, indicating the previous existence of massive accretion. The thermal history, which significantly affects the chemistry, between substellar objects with a continuous low accretion rate and objects in a quiescent phase after massive accretion (outburst) must be greatly different. In this study, the chemical evolution has been calculated in an episodic accretion model to show that CO and $N_2H^+$ have a relation different from starless cores or Class 0/I objects. Furthermore, the $CO_2$ ice feature at $15.2{\mu}m$ will be a good tracer of the thermal process in VeLLOs.

• 천문학회보
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• 제36권1호
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• pp.77.2-77.2
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• 2011

이 연구의 목적은 7차 교육과정에서 소개된 과학적 자유탐구 활동 모형을 개발하고 이러한 자유탐구 활동모형에 대한 효과를 알아보기 전에 예비 초등교사들의 인식조사를 하는 것이다. 개발 목적은 학생들의 과학탐구 활동능력신장에 있으며, 본 연구는 천문학사에 근거한 예를 사용하였다. 연구방법으로 Lawson(2010)의 과학적 탐구추론모형을 택하였다. 천문학사에서 예를 택해 자유탐구 모형과 설문지를 개발하여 예비초등교사들의 인식조사를 실시하였다. 연구결과는, (1)대부분 예비 초등교사들은 이러한 자유탐구전략의 사용에 대한 아이디어를 좋아했으며, (2)이러한 과학적 자유탐구활동의 사용의 효과 또한 대부분의 응답자들이 잘 인식하고 있었다. (3)그럼에도 불구하고 많은 예비 초등교사들은 이러한 자유탐구 전략의 구성이 쉽지 않은 과정임을 인식하였고, 학생들에게 적합한 자유탐구활동모형의 개발을 위해서는 학생을 지도하는 교사들이 서로가 협력해야 한다고 응답하였다.

• 천문학회보
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• 제40권1호
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• pp.50.2-50.2
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• 2015

전파천문학의 불모지였던 우리나라에 전파천문학이 잉태된 것은 1980년으로 국립천문대가 발족한지 불과 6년이 지난 시점으로, 소백산 61cm 광학망원경의 광전측광관측이 궤도에 진입하던 시기였다. 우리나라에서 현대천문학이 겨우 걸음마를 할 시기에 mm파 전파망원경의 도입은 용감한 도전으로, 5년여 간 많은 우여곡절을 겪으며 1985년에 전파망원경이 설치되었다. 1985년 대덕에 14m 전파망원경을 건설하며 시작된 우리나라의 전파천문학은 지난 30년간 발전을 거듭하며 전파간섭계인 한국우주전파관측망(KVN) 건설과 태양전파망원경 설치로 이어져 AGN, 원시성 및 만기형성의 미세구조 연구, 태양폭발현상 연구 등 연구 영역을 확장하고 있다. 2015년은 14m 전파망원경 건설 30주년을 맞는 해이다. 본 발표에서는 대덕전파천문대가 지난 30년간 걸어온 발자취를 살펴보고, 이를 기반으로 한 발전방향을 논의하고자 한다.