Chemistry in disks - IX. Observations and modelling of HCO+ and DCO+ in DM Tauri R. Teague, D. Semenov, S. Guilloteau, Th. Henning, A. Dutrey, V. Wakelam, E. Chapillon and V. Pietu A&A, 574 (2015) A137 Published online: 09 February 2015 DOI: 10.1051/0004-6361/201425268