Gas dynamics around dust asymmetries in turbulent disks

TL;DR

This paper investigates the formation and observational signatures of dust-trapping vortices in turbulent protoplanetary disks dominated by VSI turbulence, using 3D hydrodynamic simulations and synthetic ALMA observations.

Contribution

It demonstrates that VSI turbulence can produce long-lived vortices capable of trapping dust, and explores their observable features compared to planet-induced vortices.

Findings

Vortices form naturally in VSI turbulent disks and trap dust effectively.

Dust vertical diffusion is reduced within vortices, enhancing dust concentration.

Projection effects can hide dust asymmetries, affecting observational detection.

Abstract

High-resolution ALMA observations have revealed asymmetric dust crescents in several protoplanetary disks, suggesting efficient dust trapping mechanisms potentially linked to gas vortices. While such features have been associated with vortices--whether induced by massive planets, turbulence , or other disk processes--their origin remains unclear. In this study, we investigate the viability of dust trapping by vortices that are self-sustained in disks dominated by Vertical Shear Instability (VSI) turbulence. We perform 3D hydrodynamic simulations using the PLUTO code with Lagrangian particles of three sizes (1 mm, 500~$\mu$m, 100~$\mu$m) to analyze the gas-dust dynamics around vortices. Our simulations reveal the formation of multiple vortices, including two characteristic large-scale, long-lived vortices that are able to capture the dust particles. We also find that dust vertical diffusion is reduced within vortices, suggesting that these structures preferentially enhance radial and azimuthal motions. Finally we generate synthetic dust continuum images at different wavelength bands and velocity residuals to compare the observable properties with ALMA observations. No clear spiral features are observed in either the synthetic dust images or the velocity residuals, unlike in vortices triggered by planets. Projection effects at high disk inclinations can obscure dust asymmetries, implying that more disks may host dust crescents than currently reported.