HERSCHEL SEARCH FOR O-2 TOWARD THE ORION BAR
文献类型：期刊论文
| 作者 | Melnick, Gary J.1; Tolls, Volker1; Goldsmith, Paul F.2; Kaufman, Michael J.3; Hollenbach, David J.4; Black, John H.5; Encrenaz, Pierre6,7; Falgarone, Edith8,9; Gerin, Maryvonne8,9; Hjalmarson, Ake5 |
| 刊名 | ASTROPHYSICAL JOURNAL
 |
| 出版日期 | 2012-06-10 |
| 卷号 | 752期号:1 |
| 关键词 | astrochemistry ISM: abundances ISM: individual objects (Orion) ISM: molecules submillimeter: ISM |
| 英文摘要 | We report the results of a search for molecular oxygen (O-2) toward the Orion Bar, a prominent photodissociation region at the southern edge of the HII region created by the luminous Trapezium stars. We observed the spectral region around the frequency of the O-2 N-J = 3(3)-1(2) transition at 487 GHz and the 5(4)-3(4) transition at 774 GHz using the Heterodyne Instrument for the Far-Infrared on the Herschel Space Observatory. Neither line was detected, but the 3 sigma upper limits established here translate to a total line-of-sight O-2 column density <1.5 x 10(16) cm(-2) for an emitting region whose temperature is between 30 K and 250 K, or <1 x 10(16) cm(-2) if the O-2 emitting region is primarily at a temperature of less than or similar to 100 K. Because the Orion Bar is oriented nearly edge-on relative to our line of sight, the observed column density is enhanced by a factor estimated to be between 4 and 20 relative to the face-on value. Our upper limits imply that the face-on O-2 column density is less than 4 x 10(15) cm(-2), a value that is below, and possibly well below, model predictions for gas with a density of 10(4)-10(5) cm-(3) exposed to a far-ultraviolet flux 10(4) times the local value, conditions inferred from previous observations of the Orion Bar. The discrepancy might be resolved if (1) the adsorption energy of O atoms to ice is greater than 800 K; (2) the total face-on AV of the Bar is less than required for O-2 to reach peak abundance; (3) the O-2 emission arises within dense clumps with a small beam filling factor; or (4) the face-on depth into the Bar where O-2 reaches its peak abundance, which is density dependent, corresponds to a sky position different from that sampled by our Herschel beams. |
| 收录类别 | SCI |
| 语种 | 英语 |
| WOS记录号 | WOS:000305463400026 |
| 源URL | [http://ir.bao.ac.cn/handle/114a11/6220]  |
| 专题 | 国家天文台_射电天文研究部 |
| 作者单位 | 1.Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA 2.CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA 3.San Jose State Univ, Dept Phys & Astron, San Jose, CA 95192 USA 4.SETI Inst, Mountain View, CA 94043 USA 5.Chalmers, Dept Earth & Space Sci, Onsala Space Observ, SE-43992 Onsala, Sweden 6.Observ Paris, LERMA, F-75014 Paris, France 7.Observ Paris, CNRS, UMR8112, LRA LERMA, F-75014 Paris, France 8.Observ Paris, CNRS, UMR8112, LRA LERMA, F-75231 Paris 05, France 9.Ecole Normale Super, F-75231 Paris 05, France 10.Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China |
| 推荐引用方式 GB/T 7714 | Melnick, Gary J.,Tolls, Volker,Goldsmith, Paul F.,et al. HERSCHEL SEARCH FOR O-2 TOWARD THE ORION BAR[J]. ASTROPHYSICAL JOURNAL,2012,752(1). |
| APA | Melnick, Gary J..,Tolls, Volker.,Goldsmith, Paul F..,Kaufman, Michael J..,Hollenbach, David J..,...&van Dishoeck, Ewine F..(2012).HERSCHEL SEARCH FOR O-2 TOWARD THE ORION BAR.ASTROPHYSICAL JOURNAL,752(1). |
| MLA | Melnick, Gary J.,et al."HERSCHEL SEARCH FOR O-2 TOWARD THE ORION BAR".ASTROPHYSICAL JOURNAL 752.1(2012). |
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来源：国家天文台
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