The Observability Of Vortex-Driven Spiral Arms In Protoplanetary Disk: Basic Spiral Properties

TL;DR

This study investigates the properties of vortex-driven spiral arms in protoplanetary disks using hydrodynamics simulations, finding they are less detectable in current observations and unlikely to explain observed prominent spirals.

Contribution

It provides the first detailed analysis of vortex-driven spiral properties and compares them with planet-induced spirals, highlighting their differences and observational limitations.

Findings

Vortex-driven spirals have surface density contrasts similar to sub-thermal mass planets.

These spirals are not sensitive to vortex mass.

Current observations are unlikely to detect vortex-driven spirals.

Abstract

Some circumstellar disks are observed to show prominent spiral arms in infrared scattered light or (sub-)millimeter dust continuum. The spirals might be formed from self-gravity, shadows, or planet-disk interactions. Recently, it was hypothesized that massive vortices can drive spiral arms in protoplanetary disks in a way analogous to planets. In this paper, we study the basic properties of vortex-driven spirals by the Rossby Wave Instability in 2D hydrodynamics simulations. We study how the surface density contrast, the number, and the shape of vortex-driven spirals depend on the properties of the vortex. We also compare vortex-driven spirals with those induced by planets. The surface density contrast of vortex-driven spirals in our simulations are comparable to those driven by a sub-thermal mass planet, typically a few to a few tens of Earth masses. In addition, different from the latter, the former is not sensitive to the mass of the vortex. Vortex-driven spiral arms are not expected to be detectable in current scattered light observations, and the prominent spirals observed in scattered light in a few protoplanetary disks, such as SAO 206462 (HD 135344B), MWC 758, and LkHa 330, are unlikely to be induced by the candidate vortices in them.