2006A&A...454L..99V


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.10CEST05:00:47

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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Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 680 0
2 NAME [BM89] L1544 cor 05 04 22.5 +25 11 36           ~ 434 1
3 NAME Sgr A Region reg 17 45 12 -28 48.3           ~ 916 0
4 GCIRS 3 * 17 45 39.80 -29 00 23.9           ~ 140 0
5 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11540 0
6 WR 102dc WR* 17 46 14.69 -28 49 40.7           WC9d+OB 50 0
7 NAME Sgr B2 (North) Rad 17 47 20.2 -28 22 21           ~ 514 1
8 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 1909 1
9 NAME Sgr B2 (South) HII 17 47 20.430 -28 23 45.06           ~ 85 0
10 NAME Sgr B2 Main Rad 17 47 20.5 -28 23 06           ~ 331 1
11 NAME Sgr B2 (OH) MoC 17 47 20.8 -28 23 32           ~ 80 0
12 NAME dze Per Cloud Cld ~ ~           ~ 21 0

    Equat.    Gal    SGal    Ecl

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2020.07.10-05:00:47

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