Comparison of different orders of the baseline used to extract [¹³C II] hyperfine components for cluster 1 and cluster 3. Colored stepped data are the combined and scaled [¹³C II] spectra subtracted by the baseline with the first and second-order polynomial. Curves with corresponding colors are the fit to the [¹³C II] spectra using two Gaussian profiles, and derived optical depths of [C II] are shown as data points with error bars.