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

doi:10.1051/0004-6361/201936661

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	NH3 (1,1) hyperfine intensity anomalies in the Orion A molecular cloud
	Zhou, Dong-dong 1,3; Wu, Gang 2,3; Esimbek, Jarken 2,3; Henkel, Christian 3,5,6; Zhou, Jian-jun 2,3; Li, Da-lei 2,3; Ji, Wei-guang 3; Zheng, Xing-wu 4
刊名	ASTRONOMY & ASTROPHYSICS
	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
DOI	10.1051/0004-6361/201936661
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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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关键词	DENSE CORES ; DARK CLOUDS ; AMMONIA ; VELOCITY ; REGIONS
WOS研究方向	Astronomy & Astrophysics
语种	英语
出版者	EDP SCIENCES S A
WOS记录号	WOS:000565702000002
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
内容类型	期刊论文
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.Univ Chinese Acad Sci, 19A Yuquan Rd, Beijing 100049, Peoples R China 2.Chinese Acad Sci, Key Lab Radio Astron, Urumqi 830011, Peoples R China 3.Chinese Acad Sci, Xinjiang Astron Observ, 150,Sci 1 St, Urumqi 830011, Xinjiang, Peoples R China 4.Nanjing Univ, Sch Astron & Space Sci, 163 Xianlin Ave, Nanjing 210023, Peoples R China 5.King Abdulaziz Univ, Astron Dept, POB 80203, Jeddah 21589, Saudi Arabia 6.Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany
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.