Normalized [O III]λ5007 Å line (solid black), stacked H₂ line (solid red), and H I 21 cm line (solid blue) in velocity space. Each line is normalized with respect to its maximum value. The zero velocity along the x-axis is the systemic velocity of the galaxy as extracted in Sect. 3.1 and is marked with the black vertical dashed line. The H I line has been observed in absorption by Véron-Cetty et al. (2000) and is reproduced as an emission line using a Gaussian function and the parameters reported in the text.