Investigating the Future Potential of an Upgraded ALMA to Image Planet Forming Disks at Sub-au Scales

TL;DR

An upgraded ALMA with extended baselines could significantly improve imaging of protoplanetary disk substructures at sub-au scales, enabling detection of Earth-mass planets and their effects on disk morphology.

Contribution

This study demonstrates the potential of a proposed ALMA upgrade to resolve and detect disk features caused by Earth-mass planets at close orbital distances.

Findings

Extended ALMA can detect super-Earth gaps at 1 au.

Earth-mass planets at 2-3 au produce observable disk structures.

Simulations show improved resolution enables new planet formation insights.

Abstract

In recent years, ALMA has been able to observe large-scale substructures within protoplanetary disks. Comparison with the predictions from models of planet-disk interaction has indicated that most of these disk substructures can be explained by the presence of planets with the mass of Neptune or larger at orbital radii of $\approx 5 - 100$ au. Better resolution is needed to observe structures closer to the star, where terrestrial planets are expected to form, as well as structures opened by planets with masses lower than Neptune. We investigate the capabilities of a possible extension to ALMA that would double the longest baseline lengths in the array to detect and resolve disk substructures opened by Earth-mass and Super Earth planets at orbital radii of $1-5$ au. By simulating observations of a family of disk models using this extended configuration in ALMA Bands 6 and 7, we show that an upgraded ALMA would detect gaps in disks formed by super-Earths as close as 1 au, as well as Earth-mass planets down to $2-3$ au from the young host stars in nearby star forming regions.