Ammonia in the hot core W51-IRS2: 11 new maser lines and a maser component with a velocity drift

With the 100-m telescope at Effelsberg 19 ammonia (NH[sub 3]) maser lines have been detected toward the prominent massive star forming region W51-IRS2. Eleven of these inversion lines, the (J, K) = (6, 2), (5, 3), (7, 4), (8, 5), (7, 6), (7, 7), (9, 7), (10,7), (9, 9), (10, 9), and (12, 12) transitions, are classified as masers for the first time in outer space. Similarities in line widths and velocities indicate that such groups of maser lines arise from the same regions, which can be explained by pumping through vibrational excitation. The large number of NH[sub 3] maser lines in W51-IR52 is most likely related to the exceptionally higb kinetic temperature and NH3 column density of this young massive star forming region.