Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sagittarius B2(M)

H2O+ has been observed in its ortho- and para- states toward the massive star forming core Sgr B2(M), located close to the Galactic center. The observations show absorption in all spiral arm clouds between the Sun and Sgr B2. The average o/p ratio of H2O+ in most velocity intervals is 4.8, which cor...

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Published inAstronomy and astrophysics (Berlin) Vol. 521
Main Authors Schilke, P., Comito, C., Müller, H. S. P., Bergin, E. A., Herbst, E., Lis, D. C., Neufeld, D. A., Phillips, T. G., Bell, T. A., Blake, G. A., Cabrit, S., Caux, E., Ceccarelli, C., Cernicharo, J., Crockett, N. R., Daniel, F., Dubernet, M.-L., Emprechtinger, M., Encrenaz, P., Falgarone, E., Gerin, M., Giesen, T. F., Goicoechea, J. R., Goldsmith, P. F., Gupta, H. C., Joblin, C., Johnstone, D., Langer, W. D., Latter, W. B., Lord, S. D., Maret, S., Martin, P. G., Melnick, G. J., Menten, K. M., Morris, P., Murphy, J. A., Ossenkopf, V., Pagani, L., Pearson, J. C., Pérault, M., Plume, R., Qin, S.-L., Salez, M., Schlemmer, S., Stutzki, J., Trappe, N., van Der Tak, F. F. S., Vastel, C., Wang, S., Yorke, H. W., Yu, S., Erickson, N., Maiwald, F. W., Kooi, J., Karpov, A., Zmuidzinas, J., Boogert, A., Schieder, R., Zaal, P.
Format Journal Article
LanguageEnglish
Published EDP Sciences 01.10.2010
Subjects
Astrophysics
Galactic Astrophysics
Physics
Sciences of the Universe
line: profiles
molecular processes
astrochemistry
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Summary:H2O+ has been observed in its ortho- and para- states toward the massive star forming core Sgr B2(M), located close to the Galactic center. The observations show absorption in all spiral arm clouds between the Sun and Sgr B2. The average o/p ratio of H2O+ in most velocity intervals is 4.8, which corresponds to a nuclear spin temperature of 21 K. The relationship of this spin temperature to the formation temperature and current physical temperature of the gas hosting H2O+ is discussed, but no firm conclusion is reached. In the velocity interval 0-60 km s-1, an ortho/para ratio of below unity is found, but if this is due to an artifact of contamination by other species or real is not clear. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix (pages 6, 7) is only available in electronic form at www.aanda.org
ISSN:0004-6361
1432-0756
DOI:10.1051/0004-6361/201015087