Gas dynamics around dust asymmetries in turbulent disks

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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 performed 3D hydrodynamic simulations using the PLUTO code with Lagrangian particles of three sizes (1 mm, 500 μm, and 100 μm) to analyze the gas–dust dynamics around vortices. Our simulations revealed the formation of multiple vortices, including two characteristic large-scale, long-lived vortices that are able to capture the dust particles. We also found that dust vertical diffusion was reduced by a factor of approximately three within vortices compared to the surrounding disk, suggesting that these structures preferentially enhanced radial and azimuthal motions. Finally we generated synthetic dust continuum images at different wavelength bands and velocity residuals to compare the observable properties with ALMA observations. No clear spiral features were 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.

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