Meso-scale Instability Triggered by Dust Feedback in Dusty Rings: Origin and Observational Implications

Dusty spirals triggered by shadows in transition discs

Context. Despite the recent discovery of spiral-shaped features in protoplanetary discs in the near-infrared and millimetric wavelengths, there is still an active discussion to understand how they formed. In fact, the spiral waves observed in discs around young stars can be due to different physical mechanisms: planet/companion torques, gravitational perturbations or illumination effects. Aims. We study the spirals formed in the gaseous phase due to two diametrically opposed shadows cast at fixed disc locations. The shadows are created by an inclined non-precessing disc inside the cavity, whic…

Channels for streaming instability in dusty discs

Streaming instability is a privileged channel to bridge the gap between collisional growth of dust grains and planetesimal formation triggered by gravity. This instability is thought to develop through its secular mode, which is long-time growing and may not develop easily in real discs. We address this point by revisiting its perturbation analysis. A third-order expansion with respect to the Stokes number reveals important features over-looked so far. The secular mode can be stable. Epicycles can be unstable, more resistant to viscosity and are identified by Green's function analysis as promi…

Comparing simulations of ionisation triggered star formation and observations in RCW 120

Massive clumps within the swept-up shells of bubbles, like that surrounding the galactic HII region RCW 120, have been interpreted in terms of the Collect and Collapse (C&C) mechanism for triggered star formation. The cold, dusty clumps surrounding RCW 120 are arranged in an almost spherical shell and harbour many young stellar objects. By performing high-resolution, three-dimensional SPH simulations of HII regions expanding into fractal molecular clouds, we investigate whether the formation of massive clumps in dense, swept-up shells necessarily requires the C&C mechanism. In a second step, w…

Toroidal vortices as a solution to the dust migration problem

In an earlier letter, we reported that dust settling in protoplanetary discs may lead to a dynamical dust-gas instability that produces global toroidal vortices. In this letter, we investigate the evolution of a dusty protoplanetary disc with two different dust species (1 mm and 50 cm dust grains), under the presence of the instability. We show how toroidal vortices, triggered by the interaction of mm grains with the gas, stop the radial migration of metre-sized dust, potentially offering a natural and efficient solution to the dust migration problem.

A Disk-Wind Model for the Near-Infrared Excess Emission in Protostars

Protostellar systems, ranging from low-luminosity T Tauri and Herbig Ae stars to high-luminosity Herbig Be stars, exhibit a near-infrared (NIR) excess in their spectra that is dominated by a bump in the monochromatic luminosity with a peak near 3 microns. The bump can be approximated by a thermal emission component of temperature 1500 K that is of the order of the sublimation temperature of interstellar dust grains. In the currently popular "puffed up rim" scenario, the bump represents stellar radiation that propagates through the optically thin inner region of the surrounding accretion disk a…

ALMA观测以解析外行星 Kuiper �带亚结构（ARKS）I：动机、样本、数据处理和结果概述

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) I: Motivation, sample, data reduction, and results overview

ARKS项目通过ALMA观测揭示外行星Kuiper带的尘埃盘结构多样性，发现多个尘埃环、非高斯垂直分布及CO气体动力学特征。