Observational Signatures of Circumbinary Discs II: Kinematic Signatures in Velocity Residuals

TL;DR

This paper investigates the kinematic signatures in velocity residuals of circumbinary discs, identifying features like Doppler-flips and vortices, and compares simulations with observations to detect binarity in protoplanetary discs.

Contribution

It characterizes specific kinematic signatures of circumbinary discs and demonstrates their use in identifying binarity in observed protoplanetary systems.

Findings

Doppler-flips are not necessarily centered on a companion and can extend to the cavity edge.

Simulated kinematic signatures match observed features in HD 100546 and HD 142527.

Evidence of binarity found in disks previously considered circumstellar, like AB Aurigae.

Abstract

Kinematic studies of protoplanetary discs are a valuable method for uncovering hidden companions. In the first paper of this series, we presented five morphological and kinematic criteria that aid in asserting the binary nature of a protoplanetary disc. In this work we study the kinematic signatures of circumbinary discs in the residuals of their velocity maps. We show that Doppler-flips, spiral arms, eccentric gas motion, fast flows inside of the cavity, and vortex-like kinematic signatures are commonly observed. Unlike in the planetary mass companion case, Doppler-flips in circumbinary discs are not necessarily centred on a companion, and can extend towards the cavity edge. We then compare the kinematic signatures in our simulations with observations and see similarities to the Doppler-flip signal in HD 100546 and the vortex-like kinematic signatures in HD 142527. Our analysis also reveals kinematic evidence for binarity in several protoplantary disks typically regarded as circumstellar rather than circumbinary, including AB Aurigae and HD 100546.