Measured absorption and emission spectra, T^on and T^off, with their respective errors, and derived quantities, optical depth, spin temperature, and H i column density for the PRISMAS program source W 51, sight line P39. For a detailed description see text. The labels CL 1 and CL 3 refer to the 1σ and 3σ confidence intervals, i.e., the 68% and 99.7% distribution percentiles (see also text).