Comparison between the total column density of NH₂D, N(NH₂D), and NH₃, N(NH₃). Blue symbols correspond to HMSCs (triangles: warm cores, see Sect. 2); green squares show HMPOs (open squares are upper limits); black pentagons correspond to UC Hii regions. In most cases, the error bars are barely visible because comparable to (or smaller than) the size of the symbol. The straight lines represent the loci of D_frac(NH₃) = 0.01 and 0.1.