• 천문학회보
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• 제46권2호
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• pp.42.3-43
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• 2021

At high redshift, unlike local, many galaxy clusters are still at their stages of building. Likewise, they show a wide range in their star formation properties: some are still forming stars actively unlike their local counterparts, while others have very low level of star formation already. Here we report the two high-redshift (z~1) galaxy clusters, confirmed via Magellan MOS observation. While existing at similar redshift and having similar mass, these two clusters show very different quiescent galaxy fraction. The origin of this difference is investigated, and will be presented in the presentation.

• 천문학회보
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• 제27권1호
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• pp.21-21
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• 2002

• 한국지구과학회:학술대회논문집
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• 한국지구과학회 2010년도 춘계학술발표회 논문집
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• pp.118-119
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• 2010

별탄생에 관한 연구는 최근 천문학 영역에서 활발히 진행되고 있으며, 별이 실제로 동역학적 과정을 거쳐 형성되고 분자운의 난류적 특성에 강하게 영향을 받는다는 것을 보여주고 있다. 별탄생 과정에 관한 관측적 영역에서 상당한 진전이 있음에도 불구하고, 별탄생의 초기단계는 여전히 해결되고 있지 않다. 따라서, 별 탄생의 복잡한 역학적 특성으로 인해 컴퓨터 시뮬레이션은 별탄생 연구의 중요한 도구로 사용된다. 우리는 SPH 시뮬레이션을 활용하여 낮은 질량의 별 탄생 과정을 제시하였고, 가장 진보된 dragon code를 사용하였다. 질량과 난류, 중심 밀도 등의 값을 변화시키면서 내부 특성의 변화를 살펴보고, 어떻게 진화하는지에 대해 알아보고자 한다. (질량범위는 0.1$5\;M{\odot}$) 이 결과에 근거하여 그들의 환경조건과 특성 그리고 성간운에서 낮은 질량의 별이 탄생하는 동안 어떻게 진화하는지에 대해 논의하고자 한다.

• 천문학회보
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• 제41권2호
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• pp.34.3-35
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• 2016

Ram pressure stripping of early-type galaxies has been largely neglected until now because of their gas poor nature. MUSE IFU observation vividly reveal the presence of star-forming blobs and ionised gas tails, around an early-type galaxy in Abell 2670. The galaxy was identified as a post-merger galaxy with disturbed faint features, in MOSAIC 2 deep optical images. The imaging also revealed a series of star-forming blobs, situated in the direction facing away from the cluster centre. Thanks to the revolutionary wide field-of-view of the MUSE, combined with 8.2-m VLT (UT-4) at Cerro Paranal, we could simultaneously obtain IFU spectra of the blobs, as well as the galaxy. The MUSE spectra clearly confirms that the star-forming blobs are associated with the early-type galaxy. Moreover, MUSE reveals long ionised-gas tails, emanating from the galaxy. The quantity of gas indicates a gas rich progenitor has merged with the early-type galaxy. However the direction of the tails and blobs, and the blob morphology, appears to indicate that strong ram-pressure stripping may have stripped out gas brought in by the merger. We will present kinematic structure of the whole system (the galaxy, star-forming blobs, and gas tails), as well as the star formation history of the system, supporting a scenario where a recent galaxy merger is subjected to cluster environmental mechanisms.

• 한국지구과학회지
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• 제38권1호
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• pp.1-10
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• 2017

공생별 AG Peg는 적색거성(GS)과 백색왜성(WD)으로 구성된 성운으로 둘러싸인 쌍성계이다. AG Peg의 분광자료는 1998년, 2001년, 그리고 2002년의 세 시기에 미국 Lick 천문대에서 관측한 자료로 HI 발머 방출선 자료를 분석하였다. AG Peg의 선세기와 폭은 각 시기에 따라 변하는데, $H{\alpha}$와 $H{\beta}$ 선에서 모두 청색편이, 적색편이, 넓은 폭 성분이 나타났다. 가스 성운의 운동학적 특성을 보여주는 방출선은 WD주변에 형성된 강착원반의 반경이 매우 큼을 보여준다. 관측자의 시선 방향을 고려하면, 1998년 관측은 AG Peg의 GS와 WD가 나란히 하늘에 있는 반면, 2002년에는 WD가 GS의 전면에, 2001년에는 WD가 GS의 뒷면에 위치하였다. 이러한 상대적인 위치와 분광선의 변화를 고려하여, 우리는 GS에서 WD로의 가스유입이 지속적으로 이루어지고, 그 결과 형성된 두꺼운 원반의 회전이 관측된 분광선 윤곽의 형성을 가져온 것으로 결론지었다.

• 천문학회보
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• 제38권2호
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• pp.67.1-67.1
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• 2013

It has been known that HCN is one of ubiquitous high-density gas tracer, and the abundance ratio between HCN and its Isomer, HNC sensitively depends on kinetic temperature in star-forming regions. Here we investigate the molecular abundance ratio toward three different evolutionary phases of massive star formation: Infrared Dark Clouds, High-mass Protostellar Objects and Ultracompact HII Regions. We obtained the abundances of HCN and HNC using optically thin H13CN and HN13C lines observed with the KVN single-dish telescopes and MAMBO 1.2mm and SCUBA $850{\mu}m$ continuum data. According to our results, the ratio of [HCN]/[HNC] increases statistically with the evolutionary stage, indicative of the effect of temperature. We also found a strong anti-correlation between the column density of molecular hydrogen and the HNC abundance.

• Journal of information and communication convergence engineering
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• 제6권3호
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• pp.249-254
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• 2008

Moored ocean buoys are technically feasible approach for making sustained time series observation in the oceans and will be an important component of any long-term ocean observing system. The 3M disc buoy carried Zeno 3200, MCCB, Orbcomm, Global Star and Bluetooth module. The deployments have relied on Orbcomm and Global Star as the primary satellite communications system. In addition to detailing our practical experience in the use of Orbcomm and Global Star as high latitudes, we will present some of scientific sensor results regarding real-time oceanographic and meteorological parameters such as wind speed, wave height and etc. In this paper we present the design and implementation of a small-scale buoy sensor network. One of the major challenges is that the network is hard to access after its deployment and hence both hardware and software must be robust and reliable.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.894-896
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• 2003

Koh Chang Island is located near the east border of Thailand. The government of Thailand promotes the island as a model of eco-tourism spots. The Island undeveloped until recent years, is expected to change to major tourist attraction. 'Digital Koh Chang project' has thus. The main objective of this project is to monitor the environment and land use status of the island and to support its sound development. In March 2003, a field survey of this project was planned and field data were collected using both airborne and ground platforms and an ocean vessel. These data were combined with satellite data in the laboratory. This presentation is all balloon-born system field operation. A 5-meter length balloon filled with Helium gas was used, whose payload consisted of two RGB standard color digital still cameras, two directional rotating servo motors, a camera mount cradle as well as signal transmitting and receiving components. A series of aerial high-resolution digital images were rather easily obtained using this inexpensive system, making it possible to monitor intended landscape features in a specific field. Design of simple, low-cost and easily transportable flying platforms and local field surveys using them are useful for getting local ground truth data to calibrate satellite or airborne-based RS data. The design analysis to upgrade the system is further investigated.

• International Journal of Aeronautical and Space Sciences
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• 제14권1호
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• pp.91-98
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• 2013

The rigorous requirements of modern spacecraft missions necessitate a precise attitude determination strategy. This paper mainly researches that, based on three space-borne attitude sensors: 3-axis rate gyros, 3-antenna GPS receiver and star-sensor. To obtain global attitude estimation after an information fusion process, a feedback-involved Federated Kalman Filter (FKF), consisting of two subsystem Kalman filters (Gyros/GPS and Gyros/Star-sensor), is established. In these filters, the state equation is implemented according to the spacecraft's kinematic attitude model, while the residual error models of GPS and star-sensor observed attitude are utilized, to establish two observation equations, respectively. Taking the sensors' different update rates into account, these two subsystem filters are conducted under a variable step size state prediction method. To improve the fault tolerant capacity of the attitude determination system, this paper designs malfunction warning factors, based on the principle of ${\chi}^2$ residual verification. Mathematical simulation indicates that the information fusion strategy overwhelms the disadvantages of each sensor, acquiring global attitude estimation with precision at a 2-arcsecs level. Although a subsystem encounters malfunction, FKF still reaches precise and stable accuracy. In this process, malfunction warning factors advice malfunctions correctly and effectively.

• 천문학회지
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• 제35권4호
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• pp.209-220
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• 2002

In order to increase the completeness of the investigations of stellar abundances, we can use spectrum synthesis method, new atomic data and observation of stellar spectra with resolution comparable to solar spectral atlases. We made a brief review of main problems of these three ways. We present new results of abundance determinations in the atmospheres of four stars. The first is the implementation of new atomic data to well known Przybylski's star. We show that the number of spectral lines, which can be identificated in the spectrum of this star, can be significantly higher. The second example is the investigation of $\zeta$ Cyg. We found the abundances of 51 elements in the atmosphere of this mild barium star. The third example is halo star HD221170. Our preliminary abundance pattern consists of 42 elements. The heaviest elements in this pattern are U and Th. The last star is the spectroscopic binary HD153720. The number of elements investigated in the spectra of components of this star is not large, but the results show that the components are Am-stars.