IRAM PdBI continuum-subtracted maps of the blue- (top panels) and red- (bottom panels) shifted [C ii] 158 μm emission of SDSS J1148+5251, obtained at different velocities. The corresponding velocity integration ranges are indicated on each map. Negative and positive contours are in steps of 1.5σ. In all panels the big central cross indicates the pointing and phase centre, corresponding to the optical position of the quasar. The small crosses mark the position of the 48 blobs that we identified as belonging to the outflow. For each of these clumps in outflow we estimate the dynamical time scale τ_dyn = R/v, where R is the distance from the quasar position, and v is the average velocity of each map.