IRAM PdBI continuum-subtracted map of the total [C ii] 158 μm emission of SDSS J1148+5251, integrated within v ∈ ( − 1400,1200) km s^-1, along with spectra extracted from different positions on the source. Negative and positive contours are in steps of 3σ (1σ rms noise is 0.26 Jy beam^-1 km s^-1). For display purposes, the spectra have been re-binned by a factor of 4, corresponding to channels of 93.6 km s^-1. The Gaussian fits to the line profiles are performed on the original non-binned spectra and the fits results are presented in Table B.1.