Feasibility of interferometric observations and characterization of planet-induced structures at sub au to au scales in protoplanetary disks

¹ Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstraße 15, 24118 Kiel, Germany
² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

^★ Corresponding author: lhildebrandt@astrophysik.uni-kiel.de

Received: 6 September 2024
Accepted: 11 April 2025

Abstract

Context. Interferometric observations of protoplanetary disks by VLTI and ALMA have greatly improved our understanding of the detailed structure of these planetary birthplaces. These observations have revealed a variety of large-scale disk substructures, including rings, gaps, and spirals, spanning tens to hundreds of au, supporting the predictions of planet formation models. Recent instruments, such as MATISSE at the VLTI, allow one to resolve and investigate the inner few au of protoplanetary disks in nearby star formation regions, shedding light on the traces of planet formation and evolution at these small scales.

Aims. The aim of this work is to assess the feasibility of interferometric observations of small-scale planet-induced substructures in protoplanetary disks in nearby star-forming regions. We aim to characterize these substructures in multi-wavelength and multi-epoch observations and subsequently differentiate between simulation parameters.

Methods. On the basis of 3D hydrodynamic simulations of embedded planetary companions and subsequent 3D Monte Carlo radiative transfer simulations, we calculated and analyzed interferometric observables, assuming observations with the VLTI in the K, L, M, and N bands.

Results. The hydrodynamic simulations exhibit mass-dependent planet-induced density waves that create observable substructures, most notably for the considered case of a 300 M_⊕ planet. These substructures share similarities with observed large-scale structures and feature a prominent accretion region around the embedded planet. The visibilities show a detectable variability for multi-epoch VLTI/GRAVITY and VLTI/MATISSE observations, caused by the orbital motion of the planet, that are distinguishable from other sources of variability due to their unique combination of timescale and amplitude. Additionally, the non-uniform change of the visibilities at different baselines can be used to identify asymmetric structures. Furthermore, we show that multi-wavelength observations provide an approach to identify the fainter substructures and the signal of the accretion region.