• 천문학회지
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• 제38권2호
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• pp.249-252
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• 2005

We present results of the velocity-resolved spectroscopy of the [Fe II] $\lambda$1.644${\mu}m$ emission toward outflow sources with the Subaru Telescope at the angular resolution of 0.apos;16 ${\~}$ 0.apos;5 arcseconds. The observed sources are L1551 IRS 5, DG Tau, HL Tau and RW Aur, which are located in the Taurus-Aurigae Molecular Cloud, one of the closest star forming regions (0.apos;1 = 14 AU). We were able to resolve outflow structure in the vicinity of the sources at a scale of a few tens of AU. The position-velocity diagram of each object shows two velocity components: the high velocity component (HVC: 200 - 400 km $s^{-l}$) and the low velocity component (LVC: 50 - 150 km $s^{-l}$), which are clearly distinct in space and velocity. The HVC may be a highly collimated jet presumed from its narrow velocity width and high velocity. The LVC, on the other hand, may be a widely opened disk wind inferred from its broad velocity width and low velocity. The spectrum taken perpendicular to the L1551 IRS 5 outflow at its base shows that the LVC has a spatially wide subcomponent, supporting the above interpretation. We demonstrated that the [Fe II] 1.644 $\mu$ spectroscopy is a very powerful tool for the studies of fast jets and winds that directly emanate from star-disk systems.

• 천문학논총
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• 제28권1호
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• pp.7-13
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• 2013

We present a multi-dimensional reduction method of the surveyed cube database obtained using a single- dish radio telescope in Taeduk Radio Astronomy Observatory (TRAO). The multibeam receiver system installed at the 14 m telescope in TRAO was not optimized at the initial stage, though it became more stabilized in the following season. We conducted a Galactic Plane survey using the multibeam receiver system. We show that the noise level of the first part of the survey was higher than expected, and a special reduction process seemed to be definitely required. Along with a brief review of classical methods, a multi-dimensional method of reduction is introduced; It is found that the 'background' task within IRAF (Image Reduction and Analysis Facility) can be applied to all three directions of the cube database. Various statistics of reduction results is tested using several IRAF tasks. The rms value of raw survey data is 0.241 K, and after primitive baseline subtraction and elimination of bad channel sections, the rms value turned out to be 0.210 K. After the one-dimensional reduction using 'background' task, the rms value is estimated to be 0.176 K. The average rms of the final reduced image is 0.137 K. Thus, the image quality is found to be improved about 43% using the new reduction method.

• 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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• 제46권2호
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• pp.50.1-50.1
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• 2021

The Gaia mission opens a new window to study the kinematics and dynamics of young stellar systems in detail. The kinematic properties of young stars provide vital constraints on the formation process of their host systems. Here, we present a kinematic study of the two associations Monoceros OB1 (Mon OB1) and R1 (Mon R1). Member candidates are first selected from the published list of member candidates, a compilation of OB star catalogues, and the classification of young stellar objects with the AllWISE data. According to the conventional wisdom, we selected a total of 728 members with similar proper motions at almost the same distance. Mon OB1 and Mon R1 have high levels of substructures that are also kinematically distinct. We identify six stellar groups in these associations, of which five show a pattern of expansion. In addition, the signature of rotation is found in two stellar groups of Mon OB1. Star formation history is inferred from a color-magnitude diagram. As a result, star formation in Mon OB1 has been sustained for several million years, while Mon R1 formed at almost the same epoch as the recent star formation in Mon OB1. Some old members in the outskirt of Mon OB1 have outward motions, which rules out the previously proposed outside-in star formation scenario. Star-forming regions including Mon OB1 and Mon R1 are found along a large arc-like gas structure. Hence, the formation of these two associations may originate from the hierarchical star formation along filaments in a turbulent molecular cloud.

• 천문학회보
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• 제44권2호
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• pp.68.1-68.1
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• 2019

Turbulence plays a crucial role in controlling star formation as it produces density fluctuation as well as non-thermal pressure against gravity. Therefore, turbulence controls the mode and tempo of star formation. However, despite a plenty of previous studies, the properties of turbulence remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we mapped the Orion A and the Ophiuchus clouds, in three sets of lines (13CO 1-0/C18O 1-0, HCN 1-0/HCO+ 1-0, and CS 2-1/N2H+ 1-0) with a high-velocity resolution (~0.1 km/s) using the TRAO 14-m telescope. The mean Trms for the observed maps are less than 0.25 K, and all these maps show uniform Trms values throughout the observed area. These homogeneous and high signal-to-noise ratio data provide the best chance to probe the nature of turbulence in two different star-forming clouds, the Orion A and Ophiuchus clouds. We present comparisons between the line intensities of different molecular tracers as well as the results of a Principal Component Analysis (PCA).

• 공업화학
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• 제21권5호
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• pp.542-547
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• 2010

디젤연료 및 바이오 디젤을 포함하는 디젤연료는 성분 내에 n-파라핀과 포화 지방산 메틸에스테르가 저온에서 결정화가 이루어져 연료의 저온 특성을 감소시키는 현상이 발생한다. 이러한 문제를 방지하기 위하여 많은 방법들이 알려져 있으며, 그 중에서 알킬 메타크릴레이트계 중합체가 저온유동특성을 향상시키는 첨가제로 많이 사용되고 있다. 본 연구에서는 LMA (lauryl methacrylate), SMA (stearyl methacrylate)를 각각 측쇄 구조가 다른 알킬 메타크릴레이트를 사용하여 70 : 30의 몰 비율로 라디칼 공중합체를 합성하였다. 합성된 공중합체의 구조는 $^1H$-NMR 및 FT-IR 스펙트럼으로 분석하였으며, GPC로 분자량을 측정하였다. 이 공중합체를 디젤연료에 500~1000 ppm, 바이오디젤을 5%, 20% 함유한 디젤연료(BD5 및 BD20)에 1000~10000 ppm을 각각 첨가하여 유동점, 구름점 및 저온필터막힘점 등의 저온유동특성을 조사하였다. 저온유동특성을 측정한 결과 BD5에서 SMA를 포함한 공중합체 $PSMAmR_2n$에서 첨가 전 대비 유동점 $15^{\circ}C$, 구름점 $6^{\circ}C$, 저온필터막힘점 $10^{\circ}C$ 강하되어 가장 우수한 결과를 나타냈다.