• 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.

• 한국지구과학회지
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• 제32권4호
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• pp.402-410
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• 2011

본 논문에서는 IRAS 07280-1829 적외선원과 이를 둘러싸고 있는 분자운에 대해 수행된 $^{12}CO$와 $^{13}CO$ 1-0 분자선 관측결과와 기존의 적외선 자료를 이용하여 이 적외선원의 생성환경에 관해 연구하였다. 관측자료로부터 얻어진 적외선원의 파장별 에너지분포의 기울기(${\alpha}$=1.16)와 복사온도(145 K), 그리고 광도(${\sim}2.9{\times}10^4L_{\odot}$)는 이 적외선 천체가 CLASS I형의 중량급원시성임을 의미한다. 이 적외선원방향에서 관측된 두 CO 분자선에서 보이는 넓은 속도 성분은 분자분출류의 존재를 암시한다. 적외선원을 감싸고 있으리라 짐작되는 분자운A에서 측정된 여기온도는 9-22 K, 질량은 약 ~180 $M_{\odot}$인 것으로 보아 이 분자운이 전형적인 적외선 암흑분자운(Infrared-dark clouds)의 물리적 특성을 가짐을 보았다. 이 분자운의 질량은 비리알 질량보다 10배 이상 작은 값으로 계산되었는데 이것은 여기에 어린 원시성이 이미 생성되고 있다는 관측사실에 모순된다. 이는 아마도 분자운A가 교란운동(turbulence) 혹은 강한 자기장에 의해 지배되는 환경 가운데에 중량급원시성 IRAS 07280-1829을 생성하고 있음을 의미하는 것 일수도 있는 것으로 해석하였다.

• 천문학회보
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• 제46권1호
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• pp.56.2-56.2
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• 2021

Constraining the structure and thus the fate of giant molecular clouds (GMCs), the primary sites of star formation in galaxies, is crucial to understand the evolution of galaxies themselves. Exploiting the unprecedented sensitivity and angular resolution of the Atacama Large Millimeter/sub-millimeter Array (ALMA), we have measured the spatially-resolved (~ 20 pc resolution) properties of the GMCs in two nearby late-type galaxies, NGC 5806 (SAB(s)b) and NGC 6753 ((R)SA(r)b), as part of the WISDOM project. Although these results are preliminary, we identified ~ 200 resolved GMCs in NGC 5806 within a radius of 500 pc, most within a nuclear ring structure, and ~ 400 resolved GMCs in NGC 6753 within a radius of 2 kpc, most within a flocculent spiral structure. The GMCs of NGC 5806 have similar sizes but slightly higher linewidths than clouds in the Milky Way disc. Because the GMCs also have higher surface densities, the calculated cloud Virial parameters are nevertheless about unity, suggesting that the GMCs of NGC 5806 are in gravitational equilibrium and thus long lived. This is contrary to other WISDOM results on earlier-type galaxies, where large cloud linewidths are likely due to shear associated with the local (circular) orbital motions (rather than the clouds' self-gravity), and the clouds are either marginally or not gravitationally bound. These results support the notion that spheroids alter the dynamical states of clouds (morphological quenching), that are otherwise (i.e. in galaxy discs) fairly homogenous and similar to those of the Milky Way.

• 천문학회지
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• 제22권1호
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• pp.25-30
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• 1989

We report a null detection of $^{12}CO$ emission from a sub-condensation in a High Velocity Cloud (HVC). As a consequence of this, an upper limit of $n(H_2)\frac{X(CO)}{DV/DR}{\leq}2{\times}10^{-5}$ was set. This implies that $^{12}CO$ abundance is deficient by at least a factor of 10 if the HVC is predominantly molecular, otherwise the CO abundance of the HVC might be normal.

• 천문학회지
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• 제13권1호
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• pp.9-14
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• 1980

The abundances of simple molecules are examined in terms of the time-dependent cloud evolution. The formation and destruction mechanisms of $H_2CO$ are reviewed. The average value of the fractional abundance of $H_2CO$ is derived to be in the range of $10^{-10}\;to\;5{\times}10^{-9}$. This is comparable to the observed values. The expected variations of the molecules formed from or destroyed by CO, CI, and $C^+$ whose abundances depend on the evolutionary state of the cloud are discussed.

• 천문학회보
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• 제43권2호
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• pp.51.3-51.3
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• 2018

MBM 110 is one of the molecular clouds at high Galactic latitude discovered by Magnani et al., and is one of a dozen cometary clouds in the Orion-Eridanus superbubble. We have conducted optical photometry and spectroscopy for a comprehensive study of the region. Recently released Gaia DR2 astrometric data as well as WISE mid-infrared data were used for the complete census of member stars. We select 17 member stars with $H{\alpha}$ emission and/or Li absorption. The total mass of stars in the region is only about $16M{\odot}$. We found that the star formation efficiency in the region is less than 5%. We discuss the origin of the cloud and the star formation history in MBM 110.

• 천문학회보
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• 제15권
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• pp.11.2-11.2
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• 1990

• 천문학회보
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• 제32권1호
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• pp.95.2-95.2
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• 2007

• 천문학회보
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• 제32권1호
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• pp.94.2-94.2
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• 2007

• 천문학회보
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• 제18권
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• pp.11-12
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• 1993