Tracking Dust Grains During Transport and Growth in Protoplanetary Disks

TL;DR

This study examines how dust grain growth and transport in protoplanetary disks interact, revealing that growth limits outward material movement due to rapid inward drift of large aggregates, affecting disk mixing and material distribution.

Contribution

It introduces a combined model of coagulation and transport in disks, highlighting how growth processes influence dust redistribution and material preservation.

Findings

Growth limits outward transport of dust grains.

Large aggregates drift inward rapidly due to gas drag.

Preservation of high-temperature materials may require special disk structures.

Abstract

Protoplanetary disks are dynamic objects, within which dust grains and gas are expected to be redistributed over large distances. Evidence for this redistribution is seen both in other protoplanetary disks and in our own Solar System, with high-temperature materials thought to originate close to the central star found in the cold, outer regions of the disks. While models have shown this redistribution is possible through a variety of mechanisms, these models have generally ignored the possible growth of solids via grain-grain collisions that would occur during transit. Here we investigate the interplay of coagulation and radial and vertical transport of solids in protoplanetary disks, considering cases where growth is limited by bouncing or by fragmentation. We find that in all cases, growth effectively limits the ability for materials to be carried outward or preserved at large distances from the star. This is due to solids being incorporated into large aggregates which drift inwards rapidly under the effects of gas drag. We discuss the implications for mixing in protoplanetary disks, and how the preservation of high temperature materials in outer disks may require structures or outward flow patterns to avoid them being lost via radial drift.