On the Commonality of 10-30AU Sized Axisymmetric Dust Structures in Protoplanetary Disks

TL;DR

This study reveals that small, axisymmetric dust structures of 10-30AU are common in protoplanetary disks, potentially linked to snowlines and crucial for understanding planet formation.

Contribution

It provides high-resolution ALMA observations showing widespread small-scale dust structures, highlighting their possible role in dust trapping and planet formation.

Findings

Disks exhibit ~axi-symmetric 10-30AU structures.

Enhanced emission observed beyond CO snowlines.

Small-scale structures may be due to physical gaps or opacity variations.

Abstract

An unsolved problem in step-wise core-accretion planet formation is that rapid radial drift in gas-rich protoplanetary disks should drive mm-/meter-sized particles inward to the central star before large bodies can form. One promising solution is to confine solids within small scale structures. Here we investigate dust structures in the (sub)mm continuum emission of four disks (TW Hya, HL Tau, HD 163296 and DM Tau), a sample of disks with the highest spatial resolution ALMA observations to date. We retrieve the surface brightness distributions using synthesized images and fitting visibilities with analytical functions. We find that the continuum emission of the four disks is ~axi-symmetric but rich in 10-30AU-sized radial structures, possibly due to physical gaps, surface density enhancements or localized dust opacity variations within the disks. These results suggest that small scale axi-symmetric dust structures are likely to be common, as a result of ubiquitous processes in disk evolution and planet formation. Compared with recent spatially resolved observations of CO snowlines in these same disks, all four systems show enhanced continuum emission from regions just beyond the CO condensation fronts, potentially suggesting a causal relationship between dust growth/trapping and snowlines.