P. Magain and D. Gillet
reported on the
Detection of interstellar CH and CH⁺ towards SN 1987a,
Astron. Astrophys. 184, L5–L6 (1987).
Lowest-J optical transitions were observed in absorption with the ESO 1.4 m telescope at La Silla. The velocities correspond to interstellar matter within the Large Magellanic Cloud.

E. Falgarone, M. A. Zwaan, B. Godard, E. Bergin, R. J. Ivison, P. M. Andreani, F. Bournaud, R. S. Bussmann, D. Elbaz, A. Omont, I. Oteo, and F. Walter
reported on the
Large Turbulent Reservoirs of Cold Molecular Gas around High-redshift Starburst Galaxies,
Nature 548, (1987) 430–433.
The J = 1 – 0 transitions of CH⁺ was detected in emission and/or absorption toward six galaxies at red-shifts of 2.0 to 2.6 with ALMA.

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 J = 1 – 0 transitions of CH⁺ and ¹³CH⁺ were observed with ALMA redshifted from about 835.1 and 830.2 GHz to about 442.85 and 440.24 GHz. The molecular cations were detected toward both SW and NE images. The intensity ratio appears to suggest the molecular cation resides in gas with at least slightly higher molecular fraction than H₂O⁺ or H₂Cl⁺. The ¹²C/¹³C isotopic ratio is about 100, possibly higher. This is, to the best of our knowledge, the first account on extragalactic ¹³CH⁺.

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