RADEX non-LTE modeling for NH₃. a) the integrated intensity ratio as a function of n_H2 and T_kin for a given para-NH₃ abundance per velocity gradient [X]/(dv/dr) of 4.4 × 10^-11 pc (km s^-1)^-1. b) the integrated intensity ratio as a function of [X]/(dv/dr) and T_kin for a given density of 10⁵ cm^-3. In both panels, the levels go from 0.1 to 1 by 0.1. c) the integrated intensity ratio as a function of n_H2 and T_kin for a given para-NH₃ abundance per velocity gradient [X]/(dv/dr) of 4.4 × 10^-11 pc (km s^-1)^-1. The levels start from 0.1 to 0.6 by 0.1. The red solid line and the dashed lines represent the observed line ratio as well as its lower and upper limit in Figs. 3a–c. d) the integrated intensity ratio and as a function of n_H2 and T_kin for a given ortho-NH₃ abundance per velocity gradient [X]/(dv/dr) of 5.6 × 10^-11 pc (km s^-1)^-1. The levels start from 0.05 to 0.2 by 0.05. The observed line ratio = (0.28 ± 0.08) is beyond the modeled range, indicating that the kinetic temperature is either higher than 300 K or that NH₃ (6, 6) is affected by population inversion.