Issue |
A&A
Volume 425, Number 1, October I 2004
|
|
---|---|---|
Page(s) | 151 - 162 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20040542 | |
Published online | 10 September 2004 |
Interstellar absorption lines toward Cep OB4*
Max-Planck Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany e-mail: gredel@mpia.de; gredel@caha.es
Received:
29
March
2004
Accepted:
10
June
2004
An analysis of optical echelle spectra towards nine stars in the
Cep OB4 association is presented. Interstellar absorption lines
which arise in the (1, 0) and (2, 0) bands of the CN A – X
red
system towards BD+66° 1661, BD+66° 1674, and BD+66° 1675
are used to infer accurate CN column densities N(CN). A comparison
with earlier measurements in the CN violet system allows to infer
a CN Doppler b parameter of b(CN
km s-1.
Molecular carbon absorption lines which
arise in the (1, 0), (2, 0) and (3, 0) bands of the C2 A
– X
Phillips
system is used to infer gaskinetic temperatures of
K and
densities of
cm-3 towards
BD+66° 1661 and BD+66° 1675, and a temperature of
K and a density of
cm-3 towards BD+66° 1674.
The R(1) line of the (0, 0) band of the CH A
system is detected towards 6 stars. A tight
correlation exists between N(C2) and N(CH). N(CN)
increases with N(CH) and with N(C2).
Interstellar CH+ is marginally detected towards
four stars. Inferred CH+ column densities are significantly
lower than towards other lines of sight with similar reddening.
The velocity structure towards Cep OB4 and the chemical abundances
suggest that CN, C2, CH, and CH+ are formed
in quiescent material. A previous suggestion that the molecules
form in a photon-dominated region close to the stars is not supported
by the observations.
Key words: ISM: abundances / ISM: clouds / ISM: molecules / ISM: lines and bands
© ESO, 2004
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