HO and HDO column density and column density ratio plots. The left, middle and right columns represent the plots for the blue-shifted, systemic and red-shifted components, respectively. In the first row, total column densities at different excitation temperatures are plotted in blue (HO) and red (HDO) thick curves. Their column density density ratios, shown in the second row, are plotted in thick purple curves. The thin curves represent the errors. In addition, the HO over HDO column density ratio, derived from van der Tak et al. (2006) and Wilson & Rood (1994), are plotted as green horizontal lines. The excitation temperatures for a given component can be read out by finding the intersection of the green lines and thick purple lines. The thick vertical dashed lines mark the derived temperatures for ratio 2.8 and 4.0. Here we derive the excitation temperature without considering the error of absolute flux density. Derived temperatures and column densities are summarized in Table 7.