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350 μm map of the Ophiuchus molecular cloud: core mass function

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Science China(Physics,Mechanics & Astronomy) 2015年第2期58卷 114-124页

作者： ZHANG GuoYin LI Di HYDE Ashley K QIAN Lei LYU HuaLei WU ZhongZu College of Science/Department of Physics Guizhou University Key Laboratory of Radio Astronomy Chinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences Space Science Institute Department of Astronomy California Institute of Technology Astrophysics Group Imperial College London

Stars are born in dense cores of molecular clouds. The core mass function （CMF）, which is the mass distribution of dense cores, is important for understanding the stellar initial mass function （IMF）. We obtained 350μm dust continuum data using the SHARC-II camera at the Caltech Submillimeter Observatory （CSO） telescope. A 350μm map covering 0.25 deg2 of the Ophiuchus molecular cloud was created by mosaicing 56 separate scans. The CSO telescope had an angular resolution of 9＂, corresponding to 1.2 ×103 AU at the distance of the Ophiuchus molecular cloud （131 pc）. The data was reduced using the Comprehensive Reduction Utility for SHARC-II （CRUSH）. The flux density map was analyzed using the GaussClumps algorithm, within which 75 cores has been identified. We used the Spitzer c2d catalogs to separate the cores into 63 starless cores and 12 protostellar cores. By locating Jeans instabilities, 55 prestellar cores （a subcategory of starless cores） were also identified. The excitation temperatures, which were derived from FCRAO 12CO data, help to improve the accuracy of the masses of the cores. We adopted a Monte Carlo approach to analyze the CMF with two types of functional forms; power law and log-normal. The whole and prestellar CMF are both well fitted by a log-normal distribution, with p = -1. 18 ±0.10, σ = 0.58 ± 0.05 and μ= 1.40 ＋ 0.10, σ= 0.50 ＋ 0.05 respectively. This finding suggests that turbulence influences the evolution of the Ophiuchus molecular cloud.

关键词： 1SM molecular clouds Ophiuchus CMF

J-comb: An image fusion algorithm to combine observations covering different spatial frequency ranges

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Science China(Physics,Mechanics & Astronomy) 2022年第9期65卷 138-156页

作者： Sihan Jiao Yuxin Lin Xiangyu Shui Jingwen Wu Zhiyuan Ren Di Li National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Centre for Astrochemical Studies Max-Planck-Institut f¨ur Extraterrestrische PhysikGarching 85748Germany Astrophysics Department Munich UniversityMunich 81679Germany NAOC-UKZN Computational Astrophysics Centre University of KwaZulu-NatalDurban 4000South Africa

Ground-based, high-resolution bolometric(sub)millimeter continuum mapping observations on spatially extended target sources are often subject to significant missing fluxes. This hampers accurate quantitative analyses. Missing flux can be recovered by fusing high-resolution images with observations that preserve extended structures. However, the commonly adopted image fusion approaches do not maintain the simplicity of the beam response function and do not try to elaborate the details of the yielded beam response functions. These make the comparison of the observations at multiple wavelengths not straightforward. We present a new algorithm, J-comb, which combines the high and low-resolution images linearly. By applying a taper function to the low-pass filtered image and combining it with a high-pass filtered image using proper weights, the beam response functions of our combined images are guaranteed to have near-Gaussian shapes. This makes it easy to convolve the observations at multiple wavelengths to share the same beam response functions. Moreover, we introduce a strategy to tackle the specific problem that the imaging at 850 μm from the present-date ground-based bolometric instrument and that taken with the Planck satellite do not overlap in the Fourier domain. We benchmarked our method against two other widely-used image combination algorithms, CASA-feather and MIRIAD-immerge, with mock observations of star-forming molecular clouds. We demonstrate that the performance of the J-comb algorithm is superior to those of the other two algorithms. We applied the J-comb algorithm to real observational data of the Orion A star-forming region. We successfully produced dust temperature and column density maps with ~10′′angular resolution, unveiling much greater details than the previous results. A py Thon code release of J-comb and implementation of the algorithm are available at https://***/Sihan Jiao/J-comb.

关键词： star formation molecular clouds image processing

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^(13)CO mapping study for massive molecular cloud cores

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Science China Mathematics 2001年第4期44卷 536-544页

作者：吴月芳阎慧荣王利明王均智雷成明吴京文孙金江 Astronomy Department CAS-PKU Joint Beijing Astrophysics Center Peking University Beijing China Qinghai Station Purple Mountain Observatory Chinese Academy of Sciences Delingha China

Using the newly installed SIS receiving system on the 13.7 m telescope at Qinghai Station of PMO, United Radio Astronomy of CAS, CO isotope 13 CO J=1-0 and C18 O J=1-0 lines were observed for thr ee sources S241, S39 and ON3. Results show that the three sources have massive cor es, of which the size is ～2-5 pc, masses are ～103-104 M⊙. The wid t hs of lines are also larger than those in low mass cores. And high velocity char acteristics were observed for all the sources. The V LSR distribution p resents rotation of the core in ON3. And all the three cores contain deeply embe dded forming massive stars. The young stellar objects in S241 and ON3 seem to be moving away from their birth sites.

关键词： interstellar matter molecular clouds interstellar dynamics star formation

CO observation of SNR IC 443

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Science China(Physics,Mechanics & Astronomy) 2010年第7期53卷 1357-1369页

作者： ZHANG ZhiYu GAO Yu WANG JunZhi Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China Graduate University of Chinese Academy of Sciences Beijing 100080China Astronomy Department Nanjing UniversityNanjing 210093China

We present our 12CO and 13CO mapping observations of SNR IC 443 interacting with molecular *** is the first largescale high-resolution 13CO mapping observation in the surrounding *** morphologies of IC 443 in 12CO and 13 CO are compared with the optical,infrared,Spitzer far-infrared,X-ray,and neutral atomic gas(HI).We also make comparison and analysis in the kinematics,using the date-cubes of 12CO,13CO and HI,to help distinguish the complicated gas motions in the shocked *** on the work of Wang & Scoville(1992),we present a new model to explain the coexistence of multiple shocks with different speeds in a pc-scale region at the central clump *** test this new model by analyzing the HI and CO distribution in both velocity and space *** also establish the relationship between the dissociation rate of shocked molecular gas and the shock velocity in this ***,we derive the optical depth of 12CO with the 13CO spectra in clump B,and discuss the validity of the assumption of optically thin emission for the shocked 12CO.

关键词： supernova remnant shock molecular clouds molecular spectrum IC 443