arXiv subjects

Massimiliano Bolchini

Publications and source records attributed to Massimiliano Bolchini.

2 recordsLinked to original sources

arXiv2026

Self-induced edge rings in protoplanetary disks

Observations with a high angular resolution by ALMA have revealed that substructures are ubiquitous in protoplanetary disks. Axisymmetric dust rings are the most common morphology. The profiles of some observed disks, including young disks, are smooth overall, with a localized dip or bump near the outer edge of the continuum disk that manifests as an edge ring. While embedded planets might contribute to these structures, their physical origin remains unclear. We investigated the possibility that these edge rings arise purely from radiative transfer effects at the outer edge of a protoplanetary disk. A steep surface density dust gradient at the outer edge of the disk allows stellar irradiation to penetrate more efficiently beyond the disk edge, producing a non-monotonic temperature profile characterized by a dip that is followed by a bump. We tested whether this non-monotonic temperature structure can generate and maintain a localized continuum enhancement. We coupled radiative transfer and dust evolution by iterating between the Monte Carlo radiative transfer code RADMC-3D and the dust evolution code DustPy. This framework self-consistently follows the coupled evolution of temperature, grain growth, and dust dynamics. Thermodynamic feedback at the disk edge can naturally generate and maintain localized dust enhancements resembling the edge rings that are observed in some extremely young disks. Without invoking planets or additional dynamical perturbations, this mechanism offers a plausible explanation for the first-generation ring formation. Our results highlight the importance of coupling thermodynamics and dust evolution when modeling protoplanetary disks, suggesting that thermodynamic feedback probably plays a role in shaping disk substructures.

astro-ph.EP↗

arXiv2026

Interpreting the scattering surface in protoplanetary disks

In recent years, extreme adaptive optics have enabled high-resolution, high-contrast scattered-light observations of protoplanetary disks. Interpreting these observations requires an understanding of the scattering surface, which is shaped by the distribution of small dust grains and determines how disks appear in scattered light. We aim to exploit measurements of the scattering surface height to directly constrain the masses of small dust grains in disks. Starting from radiative transfer principles, we developed a semi-analytical model of the stellar radiation path and its interaction with the disk, deriving the height of the scattering surface as a function of disk parameters such as mass, temperature, and opacity. We validated our predictions against the radiative transfer code MCFOST. Using measured scattering heights, we inferred the mass of dust in small grains and the particle size distribution for a sample of ten disks. We confirm previous results indicating that the scattering surface coincides with the region where the integrated optical depth along the stellar path is of order unity. The thermal structure of the disk significantly affects the surface height, while dust settling and anisotropic scattering have comparatively minor effects. Applying our model to observations, we measure global small-dust mass fractions of order (10^{-3}). Using dust-opacity models, we show that these values are consistent with modest grain growth ((a_{\rm max} \gtrsim 0.1,{\rm mm})) and grain-size distribution power-law indices of approximately 3--3.5, as commonly predicted by grain-growth models. Scattering-surface measurements, together with constraints on the disk thermal structure, provide a powerful method for determining the small-dust content of protoplanetary disks.

astro-ph.EP↗