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NH3 (1,1) hyperfine intensity anomalies in the Orion A molecular cloud

文献类型：期刊论文

作者Zhou, Dong-dong1,3; Wu, Gang1,2; Esimbek, Jarken1,2; Henkel, Christian1,4,5; Zhou, Jian-jun1,2; Li, Da-lei1,2; Ji, Wei-guang1; Zheng, Xing-wu6
刊名ASTRONOMY & ASTROPHYSICS
出版日期2020-08-25
卷号640页码:114
关键词stars: formation ISM: individual objects: Orion A molecular cloud ISM: molecules line: profiles radio lines: ISM
ISSN号0004-6361
DOI10.1051/0004-6361/201936661
产权排序1
英文摘要Ammonia (NH3) inversion lines, with their numerous hyperfine components, are a common tracer used in studies of molecular clouds (MCs). In local thermodynamical equilibrium, the two inner satellite lines (ISLs) and the two outer satellite lines (OSLs) of the NH3(J, K) = (1,1) transition are each predicted to have equal intensities. However, hyperfine intensity anomalies (HIAs) are observed to be omnipresent in star formation regions, a characteristic which is still not fully understood. In addressing this issue, we find that the computation method of the HIA by the ratio of the peak intensities may have defects, especially when used to process the spectra with low-velocity dispersions. Therefore, we defined the integrated HIAs of the ISLs (HIA(IS)) and OSLs (HIA(OS)) by the ratio of their redshifted to blueshifted integrated intensities (unity implies no anomaly) and developed a procedure to calculate them. Based on this procedure, we present a systematic study of the integrated HIAs in the northern part of the Orion A MC. We find that integrated HIA(IS) and HIA(OS) are commonly present in the Orion A MC and no clear distinction is found at different locations of the MC. The medians of the integrated HIA(IS) and HIA(OS) are 0.921 +/- 0.003 and 1.422 +/- 0.009, respectively, which is consistent with the HIA core model and inconsistent with the collapse or expansion (CE) model. In the selection of those 170 positions, where both integrated HIAs deviate by more than 3 sigma from unity, most (166) are characterized by HIA(IS) < 1 and HIA(OS) > 1, which suggests that the HIA core model plays a more significant role than the CE model. The remaining four positions are consistent with the CE model. We compare the integrated HIAs with the para-NH3 column density (N(para-NH3)), kinetic temperature (T-K), total velocity dispersion (sigma (v)), non-thermal velocity dispersion (sigma (NT)), and the total opacity of the NH3(J, K) = (1,1) line (tau (0)). The integrated HIA(IS) and HIA(OS) are almost independent of N(para-NH3). The integrated HIA(IS) decreases slightly from unity (no anomaly) to about 0.7 with increasing T-K, sigma (v), and sigma (NT). The integrated HIA(OS) is independent of T-K and reaches values close to unity with increasing sigma (v) and sigma (NT). The integrated HIA(IS) is almost independent of tau (0), while the integrated HIA(OS) rises with tau (0), thus showing higher anomalies. These correlations cannot be fully explained by either the HIA core nor the CE model.
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WOS关键词DENSE CORES ; DARK CLOUDS ; AMMONIA ; VELOCITY ; REGIONS
资助项目National Nature Science foundation of China[11433008] ; CAS Light of West China Program[2018-XBQNXZ-B-024] ; National Natural Science foundation of China[11603063] ; National Natural Science foundation of China[11973076] ; National Natural Science foundation of China[11703074] ; National Natural Science foundation of China[11703073] ; Youth Innovation Promotion Association CAS ; National Science Foundation[ACI-1440620] ; National Aeronautics and Space Administration's Earth Science Technology Office, Computation Technologies Project[NCC5-626]
WOS研究方向Astronomy & Astrophysics
语种英语
WOS记录号WOS:000565702000002
出版者EDP SCIENCES S A
资助机构National Nature Science foundation of China ; CAS Light of West China Program ; National Natural Science foundation of China ; Youth Innovation Promotion Association CAS ; National Science Foundation ; National Aeronautics and Space Administration's Earth Science Technology Office, Computation Technologies Project
源URL[http://ir.xao.ac.cn/handle/45760611-7/3639]  
专题恒星形成与演化研究团组
通讯作者Wu, Gang
作者单位1.Chinese Acad Sci, Xinjiang Astron Observ, 150,Sci 1 St, Urumqi 830011, Xinjiang, Peoples R China
2.Chinese Acad Sci, Key Lab Radio Astron, Urumqi 830011, Peoples R China
3.Univ Chinese Acad Sci, 19A Yuquan Rd, Beijing 100049, Peoples R China
4.Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany
5.King Abdulaziz Univ, Astron Dept, POB 80203, Jeddah 21589, Saudi Arabia
6.Nanjing Univ, Sch Astron & Space Sci, 163 Xianlin Ave, Nanjing 210023, Peoples R China
推荐引用方式
GB/T 7714		 Zhou, Dong-dong,Wu, Gang,Esimbek, Jarken,et al. NH3 (1,1) hyperfine intensity anomalies in the Orion A molecular cloud[J]. ASTRONOMY & ASTROPHYSICS,2020,640:114.
APA Zhou, Dong-dong.,Wu, Gang.,Esimbek, Jarken.,Henkel, Christian.,Zhou, Jian-jun.,...&Zheng, Xing-wu.(2020).NH3 (1,1) hyperfine intensity anomalies in the Orion A molecular cloud.ASTRONOMY & ASTROPHYSICS,640,114.
MLA Zhou, Dong-dong,et al."NH3 (1,1) hyperfine intensity anomalies in the Orion A molecular cloud".ASTRONOMY & ASTROPHYSICS 640(2020):114.

入库方式： OAI收割

来源：新疆天文台

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