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Chemical modeling of the complex organic molecules in the extended region around Sagittarius B2
Wang, Yao1,2,3,4; Du, Fujun1,2,3; Semenov, Dmitry4,5; Wang, Hongchi1,2,3; Li, Juan6
2021-04-13
Source PublicationASTRONOMY & ASTROPHYSICS
ISSN0004-6361
Volume648Pages:16
AbstractContext. The chemical differentiation of seven complex organic molecules (COMs) in the extended region around Sagittarius B2 (Sgr B2) has been previously observed: CH2OHCHO, CH3OCHO, t-HCOOH, C2H5OH, and CH3NH2 were detected both in the extended region and near the hot cores Sgr B2(N) and Sgr B2(M), while CH3OCH3 and C2H5CN were only detected near the hot cores. The density and temperature in the extended region are relatively low in comparison with Sgr B2(N) and Sgr B2(M). Different desorption mechanisms, including photodesorption, reactive desorption, and shock heating, and a few other mechanisms have been proposed to explain the observed COMs in the cold regions. However, they fail to explain the deficiency of CH3OCH3 and C2H5CN in the extended region around Sgr B2. Aims. Based on known physical properties of the extended region around Sgr B2, we explored under what physical conditions the chemical simulations can fit the observations and explain the different spatial distribution of these seven species in the extended region around Sgr B2. Methods. We used the macroscopic Monte Carlo method to perform a detailed parameter space study. A static physical model and an evolving physical model including a cold phase and a warm-up phase were used, respectively. The fiducial models adopt the observed physical parameters except for the local cosmic ray ionization rate zeta(CR). In addition to photodesorption that is included in all models, we investigated how chain reaction mechanism, shocks, an X-ray burst, enhanced reactive desorption and low diffusion barriers could affect the results of chemical modeling. Results. All gas-grain chemical models based on static physics cannot fit the observations, except for the high abundances of CH3NH2 and C2H5CN in some cases. The simulations based on evolving physical conditions can fit six COMs when T similar to 30-60 K in the warm-up phase, but the best-fit temperature is still higher than the observed dust temperature of 20 K. The best agreement between the simulations and all seven observed COMs at a lower temperature T similar to 27 K is achieved by considering a short-duration approximate to 10(2) yr X-ray burst with zeta(CR) = 1.3 x 10(-13) s(-1) at the early stage of the warm-up phase when it still has a temperature of 20 K. The reactive desorption is the key mechanism for producing these COMs and inducing the low abundances of CH3OCH3 and C2H5CN. Conclusions. We conclude that the evolution of the extended region around Sgr B2 may have begun with a cold, T <= 10 K phase followed by a warm-up phase. When its temperature reached about T similar to 20 K, an X-ray flare from the Galactic black hole Sgr A* with a short duration of no more than 100 yr was acquired, affecting strongly the Sgr B2 chemistry. The observed COMs in Sgr B2 are able to retain their observed abundances only several hundred years after such a flare, which could imply that such short-term X-rays flares occur relatively often, likely associated with the accretion activity of the Sgr A* source.
Keywordastrochemistry ISM: abundances ISM: individual objects: Sgr B2 ISM: molecules stars: formation
Funding OrganizationNational Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft
DOI10.1051/0004-6361/202140411
Language英语
Funding ProjectNational Key R&D Program of China[2017YFA0402701] ; National Natural Science Foundation of China (NSFC)[11973091] ; National Natural Science Foundation of China (NSFC)[11873094] ; National Natural Science Foundation of China (NSFC)[12041305] ; China Scholarship Council (CSC)[201906340047] ; Deutsche Forschungsgemeinschaft[SE 1962/6-1]
Funding OrganizationNational Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; China Scholarship Council (CSC) ; China Scholarship Council (CSC) ; Deutsche Forschungsgemeinschaft ; Deutsche Forschungsgemeinschaft
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000639974700004
PublisherEDP SCIENCES S A
Citation statistics
Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/78284
Collection中国科学院国家天文台
Corresponding AuthorWang, Yao; Wang, Hongchi
Affiliation1.Chinese Acad Sci, Purple Mt Observ, 10 Yuanhua Rd, Nanjing 210023, Peoples R China
2.Chinese Acad Sci, Key Lab Radio Astron, 10 Yuanhua Rd, Nanjing 210023, Peoples R China
3.Univ Sci & Technol China, Sch Astron & Space Sci, 96 Jinzhai Rd, Hefei 230026, Peoples R China
4.Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany
5.Ludwig Maximilians Univ Munchen, Dept Chem, Butenandtstr 5-13, D-81377 Munich, Germany
6.Chinese Acad Sci, Dept Radio Sci & Technol, Shanghai Astron Observ, 80 Nandan Rd, Shanghai 200030, Peoples R China
Recommended Citation
GB/T 7714
Wang, Yao,Du, Fujun,Semenov, Dmitry,et al. Chemical modeling of the complex organic molecules in the extended region around Sagittarius B2[J]. ASTRONOMY & ASTROPHYSICS,2021,648:16.
APA Wang, Yao,Du, Fujun,Semenov, Dmitry,Wang, Hongchi,&Li, Juan.(2021).Chemical modeling of the complex organic molecules in the extended region around Sagittarius B2.ASTRONOMY & ASTROPHYSICS,648,16.
MLA Wang, Yao,et al."Chemical modeling of the complex organic molecules in the extended region around Sagittarius B2".ASTRONOMY & ASTROPHYSICS 648(2021):16.
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