Dust evolution in protoplanetary disks

TL;DR

This paper reviews recent observational and theoretical advances in understanding dust evolution in protoplanetary disks, highlighting the role of pressure bumps, dust traps, and their implications for planet formation.

Contribution

It synthesizes current knowledge on dust growth barriers, observational evidence of dust substructures, and their connection to planet formation, emphasizing recent ALMA findings and associated uncertainties.

Findings

ALMA observations reveal dust rings, gaps, and crescents as evidence of pressure bumps.

Disk dust masses vary and influence initial conditions for planet formation.

Pressure bumps may facilitate grain growth beyond barriers.

Abstract

Planet formation models rely on knowledge of the physical conditions and evolutionary processes in protoplanetary disks, in particular the grain size distribution and dust growth timescales. In theoretical models, several barriers exist that prevent grain growth to pebble sizes and beyond, such as the radial drift and fragmentation. Pressure bumps have been proposed to overcome such barriers. In the past decade ALMA has revealed observational evidence for the existence of such pressure bumps in the form of dust traps, such as dust rings, gaps, cavities and crescents through high-resolution millimeter continuum data originating from thermal dust emission of pebble-sized dust grains. These substructures may be related to young protoplanets, either as the starting point or the consequence of early planet formation. Furthermore, disk dust masses have been measured for complete samples of young stars in clusters, which provide initial conditions for the solid mass budget available for planet formation. However, observational biases exist in the selection of high-resolution ALMA observations and uncertainties exist in the derivation of the disk dust mass, which both may affect the observed trends. This chapter describes the latest insights in dust evolution and disk continuum observations. Specifically, disk populations and evolutionary trends are described, as well as the uncertainties therein, and compared with exoplanet demographics.