Hot ammonia around young O-type stars - II. JVLA imaging of highly excited metastable NH3 masers in W51-NorthC. Goddi, C. Henkel, Q. Zhang, L. Zapata and T. L. WilsonA&A, 573 (2015) A109DOI: https://doi.org/10.1051/0004-6361/201424696