S. Muller, A. Beelen, J. H. Black, S. J. Curran, C. Horellou, S. Aalto,
F. Combes, M. Guélin, and C. Henkel
A precise and accurate determination of the cosmic microwave background temperature at z = 0.89
Astron. Astrophys. 551, (2013) Art. No. A109.
The famous, but unnamed foreground galaxy in direction of the quasar PKS 1830211 was studied with the Australia Telecope Compact Array (ATCA) and with the Plateau de Bure Interferometer (PdBI). ATCA observations at 7 mm revealed one significant line of HCS+, 2 1 near 45.3 GHz (rest frequency near 85.3 GHz). A detail of the spectrum (S. Muller, private communication) shows that overlap of this line with a much stronger c-C3H2 line is almost negligible. Even though only one line was observed, the detection is probably fairly secure because of the limited line density.