Robustness of N2H+ as tracer of the CO snowline M. L. R. van ’t Hoff, C. Walsh, M. Kama, S. Facchini and E. F. van Dishoeck A&A, 599 (2017) A101 Published online: 09 March 2017 DOI: 10.1051/0004-6361/201629452