• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.101-110
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• 1998

32Cyg의 B형 별 주위에 형성된 $str{\"{o}}mgren$ 구를 가정하고 공전궤도위상 0.06과 0.78에서 이론적인 선 윤곽을 계산하였다. 항성 풍의 속도분포에 따라 alfv n 파 모형의 선윤곽이 누승 함수의 속도 분포를 이용한 모형의 선 윤곽 보다 전체적으로 낮은 세기를 보였다. HII 모형은 HII 영역이 없는 경우보다 약한 선 윤곽을 보였으나 $\phi$ = 0.06에서는 HII 영역이 없는 모형이 HII 영역을 가진 모형에 비해 단지 적색편이 쪽에서만 약간의 차이를 보였다. 한편 $\phi$ = 0.79에서 HII 영역을 가진 $Alfv{\'{e}}n$ 파 모형의 선 윤곽은 적색편이와 청색 편이 쪽에서 각각 다른 속도기울기의 누승 함수 모형으로써 나타낼 수 있었다. 이는 급격한 초기 속도 기울기를 고려하여 2개의 가속영역을 가진 누승 함수 모형이라면 항성 풍의 가속과정을 고려하지 않음으로써 생기는 오차를 줄일 수 있음을 의미한다.의미한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2000년도 한국우주과학회보 제9권2호
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• pp.95-95
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• 2000

No Abstract, See Full Text

• 천문학회지
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• 제29권spc1호
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• pp.177-178
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• 1996

• 천문학회보
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• 제25권1호
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• pp.34-34
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• 2000

• 천문학회보
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• 제43권1호
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• pp.43.1-43.1
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• 2018

Star formation in galaxies predominantly takes place in giant molecular clouds (GMCs). While it is widely believed that UV radiation feedback from young massive stars can destroy natal GMCs by exciting HII regions and driving their expansion, our understanding on how this actually occurs remains incomplete. To quantitatively assess the effect of UV radiation feedback on cloud disruption, we conduct a series of theoretical studies on the dynamics of HII regions and its role in controlling the star formation efficiency (SFE) and lifetime of GMCs in a wide range of star-forming environments. We first develop a semi-analytic model for the expansion of spherical dusty HII regions driven by the combination of gas and radiation pressures, finding that GMCs in normal disk galaxies are destroyed by gas-pressure driven expansion with SFE < 10%, while more dense and massive clouds with higher SFE are disrupted primarily by radiation pressure. Next, we turn to radiation hydrodynamic simulations of GMC dispersal to allow for self-consistent star formation as well as inhomogeneous density and velocity structures arising from supersonic turbulence. For this, we develop an efficient parallel algorithm for ray tracing method, which enables us to probe a range of cloud masses and sizes. Our parameter study shows that the net SFE, lifetime (measured in units of free-fall time), and the importance of radiation pressure (relative to photoionization) increase primarily with the initial surface density of the cloud. Unlike in the idealized spherical model, we find that the dominant mass loss mechanism is photoevaporation rather than dynamical ejection and that a significant fraction of radiation escapes through low optical-depth channels. We will discuss the astronomical.

• 천문학회지
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• 제28권2호
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• pp.255-264
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• 1995

The HII region S140 and the associated molecular cloud L1204 have been observed with 10 molecular transitions, CO (1-0), $^{13}CO$ (1-0), $C^{18}O$ (1-0), CS (2-1), $HCO^+$ (1-0), HCN (1-0), SO (${2_2}-{1_1}$), $SO_2(2_{20}-3_{13})$, OCS (8-7), and $HNCO\;(4_{04}-3_{03})$ with ${\sim}50"$ angular resolutions. More than 7,000 spectra were obtained in total. The morphology of this region shows a massive fragment (the S140 core) and the extended envelope to the northeast. Several gas condensations have been identified in the envelope, having masses of ${\sim}10^{3}M_{\odot}$ and gas number densities of ${\lesssim}10^{4}cm^{-3}$ to $3{\times}10^{5}cm^{-3}$ in their cores. The column densities of the observed molecular species toward the S140 core appear to be the typical warm clouds' abundances. It seems to be that the S140 core and L1204 have been swept up by an expanding shell called the Cepheus bubble. The large value of $L_{IR}$(embedded\;stars)/$M_{cloud}\;{\sim}\;5\;L_{\odot}$/$M_{\odot}$ of the S140 core may suggest that the star formation has been stimulated by the HII region, but the shock velocity and the pressure of the region seem to give a hint of the spontaneous star formation by the self gravity.

• 천문학회보
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• 제31권1호
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• pp.59.2-59.2
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• 2006

• 천문학회보
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• 제40권2호
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• pp.53.1-53.1
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• 2015

The molecular clouds associated with bright optical HII regions Sh 254-258 are studied with the TRAO CO observations and with the WISE near-infrared emission. Based on the morphology of the clouds and the basic physical parameters derived with the LTE analysis, Pieces of evidences for physical interactions with its surroundings are investigated.

• 천문학회보
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• 제39권2호
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• pp.80.1-80.1
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• 2014

We made simultaneous surveys of 22 GHz water and 44 / 95 GHz methanol masers toward 299 high-mass protostellar objects using the Korea VLBI Network (KVN) 21-m telescope. The sources were selected from the catalog of Red MSX Source (RMS) survey. Initial selection of the sample present high-mass protostellar objects in an evolutionary phase prior to ultra-compact HII regions, which have bolometric luminosities > $10^3L_{\odot}$ but are not associated with any radio continuum emission. After the follow-up work of ongoing RMS survey, final samples contains 56 sources classified as HII regions. We performed a simultaneous survey of 22 GHz water and 44 GHz methanol masers in 2011 and then conducted a simultaneous survey of 22 GHz water and 44 / 95 GHz methanol masers in 2012. The primary scientific goals of these surveys are to investigate the relationship among the three masers and to explore the relationship between each maser and the central star or the parental dense core. The detection rates of two epochs are 42% and 38% for water, 25% and 26% for 44 GHz methanol, and 23% (2012 only) for 95 GHz methanol masers. We performed a statistical analysis on subsample associated with a large data found in literature. In this poster, we will the preliminary data analysis results and discuss the implications.

• 천문학회보
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• 제41권2호
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• pp.39.2-40
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• 2016

The molecular gas surrounding an H II region is thought to be a place where star formation can be induced. Such triggered star formation can arise form the overpressurization of existing density enhancements or thought the collapse of a swept up layers of material. In this talk, We will discuss the results of a study of star-formation activity associated with the outer Galaxy ring-shaped H II regions KR 7, KR 81, KR 120 and KR 140 using archival Spitzer and WISE data along with the JHK observations. We used CO data cubes from the FCRAO and TRAO in order to define extent of the molecular cloud associated each HII region. Using the infrared data sets, We identified and classified YSO populations within each molecular cloud using measures such as the class I/II ratio and YSO spatial density. Along with this, one of the main question in the study of star formation is how protostar accrete material from their parent molecular clouds and observations of infall motions are needed to provide direct evidence for accretion. Combining our observation of the YSO population distribution with time scales associated with YSO evolution and HII expansion, we investigated the possible significance of triggered star formation in the molecular cloud surrounding each region.