Similar to Figs 3 and 4 , we show radial diffusion coefficients (top panel) and cumulative fraction of dust mass (bottom panel) for run tc = 10.wosg, in which the gravitational forcing from the gas is artificially removed. At larger stopping time, the measured D_p,x without gravitational stirring are now closer to models of Youdin & Lithwick (2007) (dashed grey curve) or Cuzzi et al. (1993, dotted). The clustering effect for particles of τ_s = 0.1 observed in Fig. 3 is absent when gravitational stirring is removed.