S. Muller, H. S. P. Müller, J. H. Black, M. Gérin, F. Combes, S. Curran, E. Falgarone, M. Guélin, C. Henkel, S. Martín, K. M. Menten, E. Roueff, S. Aalto, A. Beelen, T. Wiklind, and M. A. Zwaan,
reported on the
Detection of CH⁺, SH⁺, and Their ¹³C- and ³⁴S-isotopologues toward PKS 1830–211
Astron. Astrophys. 606, (2017) Art. No. A109.

The N = 1 – 0, J = 2 – 1 fine structure transitions of SH⁺ and ³⁴SH⁺ were observed with ALMA redshifted from about 526.0 and 525.1 GHz to about 279.9 and 278.4 GHz. The molecular cations were only detected toward the SW image representing denser material with a fairly high molecular fraction overall. They were not seen toward the NE image representing less dense material with a lower molecular fraction overall. Formation of SH⁺ thus appears to require higher densities than that best suited for OH⁺ or H₂O⁺.

The ³²S/³⁴S isotopic ratio is 16.2 ± 1.3, lower than the terrestrial ratio of 22, thus suggesting greater importance of supernovae in the elemental synthesis about 7.5 billion years ago compared to today. On the other hand, the ³²S/³⁴S isotopic ratios are still lower, about 10.5, for CS and H₂S in that galaxy, suggesting an even greater importance of higher-mass supernovae in the probably still denser ISM where these two molecules reside.

The isotopolog ³⁴SH⁺ has not yet been detected in a Galactic source.

Contributor(s): H. S. P. Müller; 11, 2017