Observing protoplanetary discs with the Square Kilometre Array -- I. Characterising pebble substructure caused by forming planets

TL;DR

This paper explores how the Square Kilometre Array can observe dust substructures in protoplanetary discs at cm wavelengths, revealing details about planet formation processes and pebble distribution.

Contribution

It demonstrates the potential of SKA1-MID to detect and analyze pebble substructures in discs at cm wavelengths with high fidelity and efficiency.

Findings

SKA1-MID can observe dust substructure at 2.4 cm with high resolution.

Visibility plane modeling reduces required integration time significantly.

Radial and azimuthal disc structures can be recovered effectively.

Abstract

High angular resolution observations of discs at mm wavelengths (on scales of a few au) are now commonplace, but there is a current lack of a comparable angular resolution for observations at cm wavelengths. This presents a significant barrier to improving our understanding of planet formation, in particular how dust grains grow from mm to cm sizes. In this paper, we examine the ability of the Square Kilometre Array (SKA) to observe dust substructure in a young, planet-forming disc at cm wavelengths. We use dusty hydrodynamics and continuum radiative transfer to predict the distribution and emission of 1 cm dust grains (or pebbles) within the disc, and simulate continuum observations with the current SKA1-MID design baseline at frequencies of 12.5 GHz (Band 5b, ~2.4 cm) on 5-10 au scales. The SKA will provide high-fidelity observations of the cm dust emission substructure in discs for integration times totalling 100's of hours. Radial structure can be obtained at a sufficient resolution and S/N from shorter (10's of hours) integration times by azimuthal averaging in the image plane. By modelling the intensity distribution directly in the visibility plane, it is possible to recover a similar level of (axisymmetric) structural detail from observations with integration times 1-2 orders of magnitude lower than required for high-fidelity imaging. Our results demonstrate that SKA1-MID will provide crucial constraints on the distribution and morphology of the raw material for building planets, the pebbles in protoplanetary discs.