Distribution of S/N^c and S/N(T_ab) for the H I spectra of the central beams (Table 3). Here, S/N(T_ab) is the ratio between the intensity of absorption dip revealed by method 2 and the spectra noise, and S/N^c is the signal-to-noise threshold required by method 1 (Sect. 5.2.2). The orange and blue squares represent the sources that can and cannot be successfully fit using method 1, respectively. The black line represents x = y. As predicted, the black line is the separation line between the two cases.