Abstract
Context. The water snow line divides dry and icy solid material in protoplanetary disks. It has been thought to significantly affect planet formation at all stages. If dry particles break up more easily than icy ones, then the snow line causes a traffic jam because small grains drift inward at lower speeds than larger pebbles. Aims. We aim to evaluate the effect of high dust concentrations around the snow line onto the gas dynamics. Methods. Using numerical simulations, we modeled the global radial evolution of an axisymmetric protoplanetary disk. Our model includes particle growth, the evaporation and recondensation of water, and the back-reaction of dust onto the gas. The model takes into account the vertical distribution of dust particles. Results. We find that the dust back-reaction can stop and even reverse the net flux of gas outside the snow line, decreasing the gas accretion rate onto the star to under 50% of its initial value. At the same time, the dust accumulates at the snow line, reaching dust-to-gas ratios of ɛ ≳ 0.8, and it delivers large amounts of water vapor towards the inner disk as the icy particles cross the snowline. However, the accumulation of dust at the snow line and the decrease in the gas accretion rate only take place if the global dust-to-gas ratio is high (ε0 ≳ 0.03), the viscous turbulence is low (αν ≲ 10−3), the disk is large enough (rc ≳ 100 au), and only during the early phases of the disk evolution (t ≲ 1 Myr). Otherwise the dust back-reaction fails to perturb the gas motion.
Highlights
Protoplanetary disks are composed of gas and dust
We aim to evaluate the effect of high dust concentrations around the snow line onto the gas dynamics
We find that the dust back-reaction can stop and even reverse the net flux of gas outside the snow line, decreasing the gas accretion rate onto the star to under 50% of its initial value
Summary
A gas disk evolves through viscous evolution driven by outward transport of angular momentum (LyndenBell & Pringle 1974) and orbits at a sub-Keplerian speed due to its own pressure support. In another view, dust particles couple to the gas motion according to their size (Nakagawa et al 1986; Takeuchi & Lin 2002) and small grains quickly follow the motion of the gas, while large boulders are decoupled from it. In regions such as dead zones (Kretke et al 2009; Pinilla et al 2016), the outer edges of gaps carved by planets (Dipierro & Laibe 2017; Kanagawa et al 2018), snow lines (Brauer et al 2008a; Estrada et al 2016; Drazkowska & Alibert 2017; Stammler et al 2017; Hyodo et al 2019), and pressure bumps in general (Pinilla et al 2012), particles can accumulate and grow to larger sizes, reaching concentrations where the dust back-reaction may be strong enough to alter the dynamics of the gas (Taki et al 2016; Onishi & Sekiya 2017; Kanagawa et al 2017; Gonzalez et al 2017; Dipierro et al 2018)
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