SIMBAD references

2010A&A...521L..10N - Astronomy and Astrophysics, volume 521, L10-10 (2010/10-1)

Herschel/HIFI observations of interstellar OH+ and H2O+ towards W49N: a probe of diffuse clouds with a small molecular fraction.

NEUFELD D.A., GOICOECHEA J.R., SONNENTRUCKER P., BLACK J.H., PEARSON J., YU S., PHILLIPS T.G., LIS D.C., DE LUCA M., HERBST E., RIMMER P., GERIN M., BELL T.A., BOULANGER F., CERNICHARO J., COUTENS A., DARTOIS E., KAZMIERCZAK M., ENCRENAZ P., FALGARONE E., GEBALLE T.R., GIESEN T., GODARD B., GOLDSMITH P.F., GRY C., GUPTA H., HENNEBELLE P., HILY-BLANT P., JOBLIN C., KOLOS R., KRELOWSKI J., MARTIN-PINTADO J., MENTEN K.M., MONJE R., MOOKERJEA B., PERAULT M., PERSSON C., PLUME R., SALEZ M., SCHLEMMER S., SCHMIDT M., STUTZKI J., TEYSSIER D., VASTEL C., CROS A., KLEIN K., LORENZANI A., PHILIPP S., SAMOSKA L.A., SHIPMAN R., TIELENS A.G.G.M., SZCZERBA R. and ZMUIDZINAS J.

Abstract (from CDS):

We report the detection of absorption by interstellar hydroxyl cations and water cations, along the sight-line to the bright continuum source W49N. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 972GHz N=1-0 transition of OH+ and the 1115GHz 111-000 transition of ortho-H2O+. The resultant spectra show absorption by ortho-H2O+, and strong absorption by OH+, in foreground material at velocities in the range 0 to 70km/s with respect to the local standard of rest. The inferred OH+/H2O+ abundance ratio ranges from ∼3 to ∼15, implying that the observed OH+ arises in clouds of small molecular fraction, in the 2-8% range. This conclusion is confirmed by the distribution of OH+ and H2O+ in Doppler velocity space, which is similar to that of atomic hydrogen, as observed by means of 21cm absorption measurements, and dissimilar from that typical of other molecular tracers. The observed OH+/H abundance ratio of a fewx10–8 suggests a cosmic ray ionization rate for atomic hydrogen of 0.6-2.4x10–16s–1, in good agreement with estimates inferred previously for diffuse clouds in the Galactic disk from observations of interstellar H3+ and other species.

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Journal keyword(s): ISM: molecules - submillimeter: ISM - astrochemistry - molecular processes

Simbad objects: 10

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