Discovery of widespread non-metastable ammonia masers in the Milky Way

Y. T. Yan, C. Henkel, K. M. Menten +8

We present the results of a search for ammonia maser emission in 119 Galactic high-mass star-forming regions (HMSFRs) known to host 22 GHz H${}_2$O maser emission. Our survey has led…