SIMBAD references

2006A&A...454L..99V - Astronomy and Astrophysics, volume 454, L99-102 (2006/8-1)

APEX mapping of H3O+ in the Sgr B2 region.

VAN DER TAK F.F.S., BELLOCHE A., SCHILKE P., GUESTEN R., PHILIPP S., COMITO C., BERGMAN P. and NYMAN L.-A.

Abstract (from CDS):

The cosmic-ray ionization rate ζCR of dense molecular clouds is a key parameter for their dynamics and chemistry. Variations of ζCR are well established, but it is unclear if these are related to source column density or to Galactic location. Using the APEX telescope, we have mapped the 364GHz line of H3O+ in the Sgr B2 region and observed the 307GHz line at selected positions. With the IRAM 30-m telescope we have observed the H218O 203GHz line at the same positions. Strong H3O+ emission is detected over a ∼3x2pc region, indicating an H3O+ column density of 1015-1016cm–2 in an 18'' beam. The H3O+ abundance of ∼3x10–9 and H3O+/H2O ratio of ∼1/50 in the Sgr B2 envelope are consistent with models with ζCR∼4x10–16s–1, 3xlower than derived from H3+ observations toward Sgr A, but 10xthat of local dense clouds. The ionization rates of interstellar clouds thus seem to be to first order determined by the ambient cosmic-ray flux, while propagation effects cause a factor of ∼3 decrease from diffuse to dense clouds.

Abstract Copyright:

Journal keyword(s): ISM: clouds - ISM: molecules - ISM: cosmic rays - molecular processes - astrochemistry

Simbad objects: 12

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2020.01.28-13:56:19

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