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Herschel observations of EXtra-Ordinary Sources (HEXOS): detecting spiral arm clouds by CH absorption lines

S. L. Qin ; P. Schilke ; C. Comito ; T. Moller ; R. Rolffs ; H. S. P. Muller ; A. Belloche ; K. M. Menten ; D. C. Lis ; T. G. Phillips ; E. A. Bergin ; T. A. Bell ; N. R. Crockett ; G. A. Blake ; S. Cabrit ; E. Caux ; C. Ceccarelli ; J. Cernicharo ; F. Daniel ; M. L. Dubernet ; M. Emprechtinger ; P. Encrenaz ; E. Falgarone ; M. Gerin ; T. F. Giesen ; J. R. Goicoechea ; P. F. Goldsmith ; H. Gupta ; E. Herbst ; C. Joblin ; D. Johnstone ; W. D. Langer ; S. D. Lord ; S. Maret ; P. G. Martin ; G. J. Melnick ; P. Morris ; J. A. Murphy ; D. A. Neufeld ; V. Ossenkopf ; L. Pagani ; J. C. Pearson ; M. Perault ; R. Plume ; M. Salez ; S. Schlemmer ; J. Stutzki ; N. Trappe ; F. F. S. van der Tak ; C. Vastel ; S. Wang ; H. W. Yorke ; S. Yu ; J. Zmuidzinas ; A. Boogert ; R. Gusten ; P. Hartogh ; N. Honingh ; A. Karpov ; J. Kooi ; J. M. Krieg ; R. Schieder ; M. C. Diez-Gonzalez ; R. Bachiller ; J. Martin-Pintado ; W. Baechtold ; Michael Olberg (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; L. H. Nordh ; J. L. Gill ; G. Chattopadhyay
Astronomy and Astrophysics (0004-6361). Vol. 521 (2010), p. Art. no. L14 .
[Artikel, refereegranskad vetenskaplig]

We have observed CH absorption lines (J = 3/2, N = 1 <- J = 1/2, N = 1) against the continuum source Sgr B2(M) using the Herschel/HIFI instrument. With the high spectral resolution and wide velocity coverage provided by HIFI, 31 CH absorption features with different radial velocities and line widths are detected and identified. The narrower line width and lower column density clouds show "spiral arm" cloud characteristics, while the absorption component with the broadest line width and highest column density corresponds to the gas from the Sgr B2 envelope. The observations show that each "spiral arm" harbors multiple velocity components, indicating that the clouds are not uniform and that they have internal structure. This line-of-sight through almost the entire Galaxy offers unique possibilities to study the basic chemistry of simple molecules in diffuse clouds, as a variety of different cloud classes are sampled simultaneously. We find that the linear relationship between CH and H-2 column densities found at lower AV by UV observations does not continue into the range of higher visual extinction. There, the curve flattens, which probably means that CH is depleted in the denser cores of these clouds.

Nyckelord: ISM: abundances, ISM: molecules, molecular clouds, sagittarius b2, cologne database, sight-line, submillimeter, spectroscopy, g10.6-0.4, chemistry, microwave, hydrogen



Denna post skapades 2010-12-27. Senast ändrad 2015-07-02.
CPL Pubid: 131849

 

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Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium

Ämnesområden

Astronomi, astrofysik och kosmologi

Chalmers infrastruktur