Contours of the collision probability obtained at 1 au in an MMSN disk with α = 10^-2 as a function of dust size and planetesimal size. The colored areas (labeled “geometric”, “hydro”, “Safronov”, “three-body” and “settling”) correspond to different interaction regimes. The top panel shows the results obtained using the same approach as Guillot et al. (2014) but corrected for a factor f_hydro (see text and compare with their Fig. 16). The bottom panel corresponds to results with the new prescriptions for the hydro model. For an easier comparison, the dashed red line marks the location of the hydro regime (corresponding to f_hydro< 0.9) in the Guillot et al. (2014) study.