Science with an ngVLA: Resolved Substructures in Protoplanetary Disks

TL;DR

This paper discusses how the next-generation VLA can observe protoplanetary disk substructures at 30-100 GHz to better understand planetesimal formation, addressing current theoretical and observational challenges.

Contribution

It highlights the unique capabilities of the ngVLA in resolving fine-scale disk features crucial for studying planetesimal formation.

Findings

ngVLA can resolve disk substructures at 1 au scales

30-100 GHz continuum effectively traces solids in disks

Observations will help reconcile planet formation theories

Abstract

Terrestrial planets and the cores of giant planets are thought to be built by the collisional agglomeration of solids spanning over 20 orders of magnitude in size within a few million years. However, there is tension between this basic picture of planet formation and standard theoretical assumptions associated with the migration of "pebbles" ($\sim$mm/cm-sized particles) in gas-rich disks and the presumably much longer timescales necessary to assemble ($\sim$km-scale) "planetesimals". To confront these potential theoretical discrepancies with observational constraints, the ideal tracer of the solids concentrated in protoplanetary disk substructures is the 30-100 GHz continuum, which strikes the best balance in sensitivity (emission still bright), optical depth (low enough to reliably estimate densities), and angular resolution (high enough to resolve fine-scale features at disk radii as small as 1 au). With its combination of sensitivity, frequency coverage, and angular resolution, the next-generation VLA will be the only facility that has the capabilities to open up this new window into the physics of planetesimal formation.