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Large-scale Spectroscopic Mapping of the ρ Ophiuchi Molecular Cloud Complex. I. The C2H-to-N2H+ Ratio as a Signpost of Cloud Characteristics
Pan,Zhichen1; Li,Di1,2,3; Chang,Qiang4; Qian,Lei1,2; Bergin,Edwin A.5; Wang,Junzhi6
2017-02-21
Source PublicationThe Astrophysical Journal
ISSN0004-637X
Volume836Issue:2
AbstractAbstract We present 2.5-square-degree C2H N?=?1–0 and N2H+ J?=?1–0 maps of the ρ Ophiuchi molecular cloud complex. These are the first large-scale maps of the ρ Ophiuchi molecular cloud complex with these two tracers. The C2H emission is spatially more extended than the N2H+ emission. One faint N2H+ clump, Oph-M, and one C2H ring, Oph-RingSW, are identified for the first time. The observed C2H-to-N2H+ abundance ratio ([C2H]/[N2H+]) varies between 5 and 110. We modeled the C2H and N2H+ abundances with 1D chemical models, which show a clear decline of [C2H]/[N2H+] with chemical age. Such an evolutionary trend is little affected by temperatures when they are below 40 K. At high density (nH?>?105 cm?3), however, the time it takes for the abundance ratio to drop at least one order of magnitude becomes less than the dynamical time (e.g., turbulence crossing time of ~105 yr). The observed [C2H]/[N2H+] difference between L1688 and L1689 can be explained by L1688 having chemically younger gas in relatively less dense regions. The observed [C2H]/[N2H+] values are the results of time evolution, accelerated at higher densities. For the relatively low density regions in L1688 where only C2H emission was detected, the gas should be chemically younger.
KeywordISM: individual objects (ρ Ophiuchi molecular cloud complex) ISM: molecules radio lines: ISM stars: formation
DOI10.3847/1538-4357/aa5c33
Language英语
WOS IDIOP:0004-637X-836-2-aa5c33
PublisherThe American Astronomical Society
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Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/36133
Collection中国科学院国家天文台
Affiliation1.National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100012, China; panzc@nao.cas.cn, dili@nao.cas.cn
2.Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, China
3.University of Chinese Academy of Sciences, 19 A Yuquan Road, Shijingshan District, Beijing, China
4.Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi 830011, China
5.Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109, USA
6.Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China
First Author AffilicationNational Astronomical Observatories, Chinese Academy of Sciences
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GB/T 7714
Pan,Zhichen,Li,Di,Chang,Qiang,et al. Large-scale Spectroscopic Mapping of the ρ Ophiuchi Molecular Cloud Complex. I. The C2H-to-N2H+ Ratio as a Signpost of Cloud Characteristics[J]. The Astrophysical Journal,2017,836(2).
APA Pan,Zhichen,Li,Di,Chang,Qiang,Qian,Lei,Bergin,Edwin A.,&Wang,Junzhi.(2017).Large-scale Spectroscopic Mapping of the ρ Ophiuchi Molecular Cloud Complex. I. The C2H-to-N2H+ Ratio as a Signpost of Cloud Characteristics.The Astrophysical Journal,836(2).
MLA Pan,Zhichen,et al."Large-scale Spectroscopic Mapping of the ρ Ophiuchi Molecular Cloud Complex. I. The C2H-to-N2H+ Ratio as a Signpost of Cloud Characteristics".The Astrophysical Journal 836.2(2017).
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