A compact concentration of large grains in the HD142527 protoplanetary dust trap

TL;DR

This study presents multifrequency observations of the HD142527 protoplanetary disk, revealing a compact concentration of centimeter-sized dust grains within a larger crescent of millimeter-sized particles, supporting dust trapping theories.

Contribution

The paper provides direct observational evidence of a compact concentration of large dust grains in a protoplanetary disk, confirming dust trapping efficiency for centimeter-sized particles.

Findings

A compact concentration of ~cm-sized grains was detected in HD142527.

Larger grains are more sharply confined than smaller grains.

Dust trapping is effective for centimeter-sized particles, leading to enhanced concentrations.

Abstract

A pathway to the formation of planetesimals, and eventually giant planets, may occur in concentrations of dust grains trapped in pressure maxima. Dramatic crescent-shaped dust concentrations have been seen in recent radio images at sub-mm wavelengths. These disk asymmetries could represent the initial phases of planet formation in the dust trap scenario, provided that grain sizes are spatially segregated. A testable prediction of azimuthal dust trapping is that progressively larger grains should be more sharply confined and furthermore the trapped grains should follow a distribution that is markedly different from the gas. However, gas tracers such as CO and the infrared emission from small grains are both very optically thick where the submm continuum originates, so observations have been unable to test the trapping predictions or to identify compact concentrations of larger grains required for planet formation by core-accretion. Here we report multifrequency observations of HD142527, from 34GHz to 700GHz, that reveal a compact concentration of ~cm-sized grains, with a few Earth masses, embedded in a large-scale crescent of ~mm-sized particles. The emission peaks at wavelengths shorter than ~1mm are optically thick and trace the temperature structure resulting from shadows cast by the inner regions. Given this temperature structure, we infer that the largest dust grains are concentrated in the 34 GHz clump. We conclude that dust trapping is efficient for approximately cm-sized grains and leads to enhanced concentrations, while the smaller grains largely reflect the gas distribution.