Detection of chloronium and measurement of the 35Cl/37Cl isotopic ratio   at z=0.89 toward PKS1830-211
  We report the first extragalactic detection of chloronium (H2Cl+), in the z=0.89 absorber in front of the lensed blazar PKS1830-211. The ion is detected through its 1_11-0_00 line along two independent lines of sight toward the North-East and South-West images of the blazar. The relative abundance of H2Cl+ is significantly higher (by a factor ~7) in the NE line of sight, which has a lower H2/H fraction, indicating that H2Cl+ preferably traces the diffuse gas component. From the ratio of the H2^35Cl+ and H2^37Cl+ absorptions toward the SW image, we measure a 35Cl/37Cl isotopic ratio of 3.1 (-0.2; +0.3) at z=0.89, similar to that observed in the Galaxy and the solar system. 
S. Muller (1), J. H. Black (1), M. Guelin (2,3), C. Henkel (4,5), F.   Combes (6), M. Gerin (3), S. Aalto (1), A. Beelen (7)...
astro-ph.GA