Cold gas radial mass flux versus bathtub model prediction. For the VELA disk galaxy sample, the cold gas radial flux mass at R_d, F_r = Rd, divided by the total cold gas mass within R_d, M_d, is plotted as a function of the scale factor, a, with the solid black line and the envelope indicating the median and 16^th − 84^th percentile variation over a bins of width 0.07. The brown dot-dashed line highlights the specific accretion rate of cold gas at the disk edge, predicted by a steady-state bathtub model and ignoring any disk-instability driven mass inflows through the disk onto the central bulge or feedback-driven outflows (see D13). For comparison, the cosmological specific accretion rate of baryons onto the halo, also derived in D13, is shown with the blue, dotted line. The good agreement between the black and the brown curves highlights the importance of accreted cold gas in explaining the dynamics of VELA disks.