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The interstellar medium:the key component in galactic evolution and modern cosmology

Research in Astronomy and Astrophysics 2019年第2期19卷 5-14页

作者： Carl Heiles Di Li Naomi McClure-Griffiths Lei Qian Shu Liu Department of Astronomy University of CaliforniaBerkeley National Astronomical Observatories Chinese Academy of Sciences Key Laboratory of FAST National Astronomical Observatories Chinese Academy of Sciences School of Astronomy and Space Science University of Chinese Academy of Sciences Research School for Astronomy & Astrophysics Australian National University

The gases of the interstellar medium(ism) possess orders of magnitude more mass than those of all the stars combined and are thus the prime component of the baryonic Universe. With L-band surface sensitivity even better than the planned phase one of the Square Kilometre Array(SKA1), the Five-hundredmeter Aperture Spherical radio Telescope(FAST) promises unprecedented insights into two of the primary components of ism, namely, atomic hydrogen(HI) and the hydroxyl molecule(OH). Here, we discuss the evolving landscape of our understanding of ism, particularly, its complex phases, the magnetic fields within, the so-called dark molecular gas(DMG), high velocity clouds and the connection between local and distant ism. We lay out, in broad strokes, several expected FAST projects, including an all northern-sky high-resolution HI survey(22 000 deg2, 3′FWHM beam, 0.2 km s^(-1)), targeted OH mapping, searching for absorption and maser signals, etc. Currently under commissioning, the commensal observing mode of FAST will be capable of simultaneously obtaining HI and pulsar data streams, making large-scale surveys in both science areas more efficient.

关键词： ism:atoms ism:individual(hydrogen) ism:molecules ism:evolution surveys

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Chempl: a playable package for modeling interstellar chemistry

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Research in Astronomy and Astrophysics 2021年第3期21卷 261-271页

作者： Fujun Du Purple Mountain Observatory and Key Laboratory of Radio Astronomy Chinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China

Astrochemical modeling is needed for understanding the formation and evolution of interstellar molecules,and for extracting physical information from spectroscopic observations of interstellar *** modeling usually involves the handling of a chemical reaction network and solution of a set of coupled nonlinear ordinary differential equations,which is traditionally done using code written in compiled languages such as Fortran or C/C++.While being computationally efficient,there is room for improvement in the ease of use and interactivity for such an *** this work we present a new public code named CHEMPL,which emphasizes interactivity in a modern Python environment,while remaining computationally *** reaction mechanisms and a three-phase formulation of gasgrain chemistry are implemented by *** is straightforward to run 0 D models with CHEMPL,and only a small amount of additional code is needed to construct 1 D or higher-dimensional chemical *** demonstrate its usage with a few astrochemically relevant examples.

关键词： astrochemistry methods:numerical ism:evolution ism:molecules

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Pilot HI survey of Planck Galactic Cold Clumps with FAST

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Research in Astronomy and Astrophysics 2020年第5期20卷 181-192页

作者： Ning-Yu Tang Pei Zuo Di Li Lei Qian Tie Liu Yue-Fang Wu Marko Krco Meng-Ting Liu You-Ling Yue Yan Zhu Hong-Fei Liu Dong-Jun Yu Jing-Hai Sun Peng Jiang Gao-Feng Pan Hui Li Heng-Qian Gan Rui Yao Shu Liu FAST Collaboration National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030ChinaShanghai 200030China East Asian Observatory HI 96720USA Department of Astronomy School of PhysicsPeking UniversityBeijing 100871China

We present a pilot HI survey of 17 Planck Galactic Cold Clumps(PGCCs)with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).HI Narrow Self-Absorption(HINSA)is an effective method to detect cold HI being mixed with molecular hydrogen H2 and improves our understanding of the atomic to molecular transition in the interstellar *** was found in 58%PGCCs that we *** column density of HINSA was found to have an intermediate correlation with that of 13CO,following log(N(HINSA))=(0.52±0.26)log(N13CO)+(10±4.1).HI abundance relative to total hydrogen[HI]/[H]has an average value of 4.4×10-3,which is about 2.8 times of the average value of previous HINSA surveys toward molecular *** clouds with total column density NH>5×1020 cm-2,an inverse correlation between HINSA abundance and total hydrogen column density is found,confirming the depletion of cold HI gas during molecular gas formation in more massive *** line width of 13CO is about 0-0.5 kms-1 larger than that of *** possible explanation of narrower non-thermal width of HINSA is that HINSA region is smaller than that of *** on an analytic model of H2 formation and H2 dissociation by cosmic ray,we found the cloud ages to be within 106.7-107.0 yr for five sources.

关键词： ism:clouds ism:evolution ism:molecules

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