Brightness temperature versus gas velocity. The black histogram corresponds to the H i emission spectrum, magenta to ¹²CO (j = 1−0), and cyan to ¹²CO (J = 2−1). The antenna temperature of H i is shown on the left vertical axis and the CO lines on the right vertical axis. The size of each bin is equal to the spectral resolution of each spectrum, i.e., 0.82, 0.16, and 0.32 km s⁻¹ for H i, CO (J = 1−0), and CO (J = 2−1) emission lines, respectively. These spectra were extracted from RA, Dec = 09:33:00, +70:09:00.