The first detection of radio recombination lines at cosmological distances K. L. Emig, P. Salas, F. de Gasperin, J. B. R. Oonk, M. C. Toribio, H. J. A. Röttgering and A. G. G. M. Tielens A&A, 622 (2019) A7 Published online: 19 February 2019 DOI: 10.1051/0004-6361/201834052