1997A&A...318..579G -
Astronomy and Astrophysics, volume 318, 579-594 (1997/2-2)
Chemical inhomogeneities in interstellar clouds: the high latitude cloud MCLD 123.5+24.9.
GERIN M., FALGARONE E., JOULAIN K., KOPP M., LE BOURLOT J., PINEAU DES FORETS G., ROUEFF E. and SCHILKE P.
Abstract (from CDS):
We report on observations designed to disclose the presence of the High Ionization Phase predicted to exist in dark clouds by chemical models (Le Bourlot et al.
1993A&A...267..233L and
1993ApJ...416L..87L). In addition to a high neutral carbon abundance, a high CS/SO abundance ratio and a low abundance of molecular ions, such a phase might be characterized by a low D/H fractionation ratio. In this paper, we present both observational and model results on the sulfur bearing molecules CS and SO, and their most abundant isotopomers, on the molecular ions HCO
+, H
13CO
+, HC
18O
+ and DCO
+. We have also taken new
13CO and C
18O data to improve the determination of the physical conditions at the observed positions. One of the two dark clouds investigated, a core in the high latitude cloud MCLD 123.5+24.9, presents surprinsingly strong CS and
34CS lines relative to its column density, together with weak DCO
+ lines. It has also a cold temperature and rather strong CCH and C
3H
2 lines. These observed features are characteristic of the presence of the High Ionization Phase along the line of sight. This cloud core might therefore be a good candidate for further investigation of this new phase of dark interstellar clouds.
Abstract Copyright:
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Journal keyword(s):
molecular processes - ISM: MCLD 123.5+24.9 (GAL 123.5+24.9) - abundances - clouds - molecules - radio lines: molecules
Simbad objects:
5
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