Top: adopted velocity profile for radial inflow. Positive velocities indicate flow inwards (towards the Galactic centre) and negative ones an outward flow. The flow velocity is everywhere zero before the assumed appearance of the bar at t = 6.5 Gyr. Profiles are given at t = 6, 8, 10 and and 12 Gyr (cyan long-dashed, blue short-dashed, green dotted and red solid, respectively). As corotation moves outwards (see text), the flow pattern moves also. Middle: corresponding mass flow profiles through radial zones r. Bottom: corresponding mass infall profiles (rate of mass infalling over the ring of radius r and width Δr = 0.5 kpc, at t = 6, 8, 10 and and 12 Gyr.