Vortices and spirals in the HD135344B transition disk

TL;DR

This study uses high-resolution ALMA observations and hydrodynamical simulations to analyze the complex vortex and spiral structures in the transition disk HD135344B, suggesting multiple planet-induced features.

Contribution

It introduces a new scenario where multiple planets and vortices explain the observed disk structures, challenging previous interpretations of the spiral arms.

Findings

Outer asymmetric dust feature aligns with a spiral arm but is not a spiral itself.

Hydrodynamical models support a planet at ~30 AU and a secondary vortex at ~75 AU.

Vortex formation and dissipation explain the observed dust ring morphology.

Abstract

In recent years spiral structures have been seen in scattered light observations and signs of vortices in millimeter images of protoplanetary disks, both probably linked with the presence of planets. We present ALMA Band 7 (335 GHz or 0.89 mm) continuum observations of the transition disk HD135344B at unprecedented spatial resolution of 0.16", using superuniform weighting. The data show that the asymmetric millimeter dust ring seen in previous work actually consists of an inner ring and an outer asymmetric structure. The outer feature is cospatial with the end of one of the spiral arms seen in scattered light, but the feature itself is not consistent with a spiral arm due to its coradiance. We propose a new possible scenario to explain the observed structures at both wavelengths. Hydrodynamical simulations show that a massive planet can generate a primary vortex (which dissipates at longer timescales, becoming an axisymmetric ring) and trigger the formation of a second generation vortex further out. Within this scenario the two spiral arms observed at scattered light originate from a planet at ~30 AU and from the secondary vortex at ~75 AU rather than a planet further out as previously reported.