CH+(1-0) and 13CH+(1-0) absorption lines in the direction of massive star-forming regions
Journal article, 2010

We report the detection of the ground-state rotational transition of the methylidyne cation CH+ and its isotopologue (CH+)-C-13 toward the remote massive star-forming regions W33A, W49N, and W51 with the HIFI instrument onboard the Herschel satellite. Both lines are seen only in absorption against the dust continuum emission of the star-forming regions. The CH+ absorption is saturated over almost the entire velocity ranges sampled by the lines-of-sight that include gas associated with the star-forming regions (SFR) and Galactic foreground material. The CH+ column densities are inferred from the optically thin components. A lower limit of the isotopic ratio [(CH+)-C-12]/[(CH+)-C-13]> 35.5 is derived from the absorptions of foreground material toward W49N. The column density ratio, N(CH+)/N(HCO+), is found to vary by at least a factor 10, between 4 and > 40, in the Galactic foreground material. Line-of-sight 12CH+ average abundances relative to total hydrogen are estimated. Their average value, N(CH+)/NH > 2.6 x 10(-8), is higher than that observed in the solar neighborhood and confirms the high abundances of CH+ in the Galactic interstellar medium. We compare this result to the predictions of turbulent dissipation regions (TDR) models and find that these high abundances can be reproduced for the inner Galaxy conditions. It is remarkable that the range of predicted N(CH+)/ N(HCO+) ratios, from 1 to similar to 50, is comparable to that observed.



ISM: kinematics and dynamics

ISM: molecules


E. Falgarone

B. Godard

J. Cernicharo

M. de Luca

M. Gerin

T.G. Phillips

John H Black

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

D. Lis

T. A. Bell

F. Boulanger

A. Coutens

E. Dartois

P. Encrenaz

T. Giesen

J.R. Goicoechea

P.F. Goldsmith

H. Gupta

C. Gry

P. Hennebelle

E. Herbst

P. Hily-Blant

C. Joblin

M. Kazmierczak

R. Kolos

J. Krelowski

J. Martin-Pintado

B. Mookerjea

D.A. Neufeld

M. Perault

J. C. Pearson

Carina Persson

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

R. Plume

M. Salez

M. Schmidt

P. Sonnentrucker

J. Stutzki

D. Teyssier

C. Vastel

S. Yu

K. M. Menten

T. R. Geballe

S. Schlemmer

R. Shipman

A.G.G.M. Tielens

S. Philipp

A. Cros

J. Zmuidzinas

L.A. Samoska

K. Klein

A. Lorenzani

R. Szczerba

I. Peron

P. Cais

P. Gaufre

L. Ravera

P. Morris

S. Lord

P. Planesas

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 521 1 Article Number: L15- L15

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences



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