Radial Gradients in Dust-to-gas Ratio Lead to Preferred Region for Giant Planet Formation

The Rosseland mean opacity of dust in protoplanetary disks is often calculated assuming the interstellar medium (ISM) size distribution and a constant dust-to-gas ratio. However, ratio are distinct from those ISM. Here, we use simple evolution models that incorporate grain growth transport to calculate time grains as function distance star. Dust dynamics sensitive assumed value turbulence strength $\alpha_{\rm t}$ velocity at which fragment $v_{\rm frag}$. For moderate-to-low strengths t} \lesssim 10^{-3}$ substantial differences frag}$ for icy ice-free grains, find spatially non-uniform deviate significantly ISM values, agreement with previous studies. effect on dominates over distribution. This varying -- non-monotonic creates region disk optimal producing hydrogen-rich planets, potentially explaining apparent peak gas giant planet occurrence rate intermediate distances. enhanced within ice line also suppresses accretion rates onto sub-Neptune cores, thus stifling their tendency undergo runaway lifetimes. Finally, our work corroborates idea low mass cores large primordial gaseous envelopes (`super-puffs') originate beyond line.