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C^(18)O Observations of the Dark Molecular Cloud L134 and Gas Depletion onto Dust

Chinese Journal of Astronomy and Astrophysics 2005年第2期5卷 144-150页

作者： Xin-Jie Mao and Xiao-Xia Sun Department of Astronomy, Beijing Normal University, Beijing 100875 maoxj@*** Department of Astronomy Beijing Normal University Beijing 100875

We map the dark molecular cloud core of L134 in the C^(18)O (J = 1 - 0)emission line using the PMO 13.7m telescope, and present a contour map of integrated intensity ofC^(18)O (J = 1 - 0) emission. The C^(18)O cloud is inside the distribution of extinction A_B, thevisual extinction of blue light, as well as inside the ^(13)CO cloud in the L134 region. Thedepletion factors in this C^(18)O cloud are generally greater than unity, which means there is gasdepletion onto dust. Since only a minimum A_B - 9.7 mag is available, and our observations measureboth undepleted and depleted regions along the line of sight, the depletion factors could verylikely be larger in the central core than the calculated value. So we conclude that depletion doesoccur in the bulk of the C^(18)O cloud through a comparison between the C^(18)O and blue extinctionmaps in the L134 region. There is no direct evidence as yet for star formation in L134, and so coreson the verge of collapse will not be visible in CO and other gas molecules.

关键词： ism: clouds ism: individual (L134) ism: molecules ism: extinction

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The Gas-to-Dust Relation in the Dark Cloud L1523-Observational Evidence for CO Gas Depletion

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Chinese Journal of Astronomy and Astrophysics 2008年第6期8卷 686-692页

作者： H.G.Kim B.G.Kim J.H.Jung Korea Astronomy and Space Science Institute 61-1 Hwaam Yuseong Daejeon 305-348 Korea

Correlation between gas and dust column density has been studied for the dark globule L1523. The 13CO（J=1→0） emission is used for tracing the gas, and the IR emissions, for tracing the dust constituent. In order to match the beam resolution between the images, a beam de-convolution algorithm based on the Maximum Correlation Method （MCM） was applied on the Infrared Astronomical Satellite （IRAS） data. The morphology of 13CO column density map shows a close correlation to that of 100μm dust optical depth. The distribution of the optical depth at 100 μm follows that of gas column density more closely than does the flux map at either 60 or 100μm. The ratio of the 13CO column density to the 100μm optical depth shows a decreasing trend with increasing dust optical depth in the central part, indicating possible molecular gas condensation onto dust particles. The excessive decrease in the CO column density in the envelope may most probably be due to the photo-dissociation of CO molecules.

关键词： ism: clouds ism: dust ism: molecules

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WISE Infrared Search for Young Stellar Objects Associated with Starless Cores

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International Journal of Astronomy and Astrophysics 2023年第2期13卷 89-111页

作者： Susumu Sato Yuri Iwamoto Yoichi Itoh Nishi-Harima Astronomical Observatory Center for Astronomy University of Hyogo Hyogo Japan

This study presents the results of an infrared search of young stellar objects (YSOs) associated with cores with high optical extinction and no associated infrared IRAS source. Four hundred YSO candidates were identified in the WISE photometric catalog based on the infrared excess attributed to the circumstellar materials and proto-planetary disks. One-hundred and forty-nine cores do not have YSO candidates. Whereas, 32 cores harbor only Class I candidates and 107 cores have Class II candidates. Ninety-one cores that were previously identified as starless cores, were found to contain YSOs. The ratio of the number of starless cores to the number of star-forming cores suggests that the typical timescale from molecular cloud core formation to the birth of a star is in the range of 0.5 - 1.4 Myr.

关键词： Stars: Formation ism: clouds Infrared: Stars

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