Top panel: integrated H₂O (1₁₀−1₀₁) line intensity plotted vs. the integrated NH₃ (1₀−0₀) line intensity. Symbols are as in Fig. 2. The solid line represents the linear fit to all points. The Spearman rank coefficient is 0.94. Middle panel: integrated NH₃ (1₀−0₀) line intensity vs. the integrated N₂H⁺ (6−5) line intensity. Source l30-304 has not been included in the plot (see text). The Spearman rank coefficient is 0.96. Bottom panel: , proportional to the H₂O line luminosity, vs. continuum temperature, T_c. Symbols are as in Fig. 2.