Issue |
A&A
Volume 380, Number 1, December II 2001
|
|
---|---|---|
Page(s) | 384 - 387 | |
Section | Catalogs and data | |
DOI | https://doi.org/10.1051/0004-6361:20011475 | |
Published online | 15 December 2001 |
Research Note On the frequency of the CS (J: 2
1) and
(J: 5
4) transitions *
1
Demirm & UMR 8540 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75140 Paris, France
2
Iram, Avda Divina Pastora, 7 Nucleo Central, 18012 Granada, Spain e-mail: tgallego@iram.es
3
University of Arizona, Steward Observatory, 933 N. Cherry Ave., Tucson, AZ 85721, USA e-mail: aapponi@as.arizona.edu
Corresponding author: L. Pagani, laurent.pagani@obspm.fr
Received:
17
July
2001
Accepted:
15
October
2001
While conducting high signal-to-noise ratio (SNR) observations
of multiple transitions and different isotopomers of CS, SO and CO
towards L183 (also known as L134N), we found that
the CS (J: 21) line frequency established by Kuiper et al. ([CITE]) during observations towards L1498 was in
disagreement with our observations. We have consequently repeated
their observations towards that object, but in a slightly different
manner by observing simultaneously the CS (J: 2
1) line
at 98 GHz and the CCS (JN: 8
) line at 94 GHz
with the same telescope and the same receivers therefore
eliminating the possibility of errors associated with either
software or hardware. We found that our L183 data was best
described with the standard frequency of 97 980.95 MHz. We also
found a real difference in the velocity position of the CS and CCS
peaks in L1498, but one only half that reported by Kuiper
et al. ([CITE]). Most importantly, we have established that
the L1498 cloud is not well-suited to set the CS
(J: 2
1) frequency despite the exceptional narrowness of
the lines. The CS (J: 2
1) line shape is far from
Gaussian and suffers from strong effects, due either to large-scale
movements (infall and/or rotation), or to self-absorption, or
both. These results and other works (Lemme et al. [CITE]; Lee
et al. [CITE]) have convinced us that these observations are
consistent with the standard CS (J: 2
1) line
frequency. We also checked the C34S (J: 2
1) and
the CS (J: 5
4) transitions and found a major
discrepancy for the latter with the JPL catalogue. Finally, CS
transitions have been recently re-measured in the laboratory by
Gottlieb et al. ([CITE]) with high precision and are found
to be consistent with our interpretation.
Key words: radio lines: ISM / ISM: molecules / ISM: individual objects: L183 / ISM: individual objects: L1498
© ESO, 2001
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