Dynamical dust traps in misaligned circumbinary discs: analytical theory and numerical simulations

TL;DR

This paper presents an analytical and numerical study of dust trap formation in misaligned circumbinary discs, revealing that differential precession causes dust pile-ups that could enhance planet formation.

Contribution

It introduces a novel mechanism for dust trap formation driven by precession rate differences, expanding understanding beyond pressure maxima in such systems.

Findings

Dust rings form due to precession rate differences between gas and dust.

Numerical simulations agree with analytical predictions across parameter space.

Dust pile-ups may promote planet formation in circumbinary discs.

Abstract

Recent observations have shown that circumbinary discs can be misaligned with respect to the binary orbital plane.The lack of spherical symmetry, together with the non-planar geometry of these systems, causes differential precession which might induce the propagation of warps. While gas dynamics in such environments is well understood, little is known about dusty discs. In this work, we analytically study the problem of dust traps formation in misaligned circumbinary discs. We find that pile-ups may be induced not by pressure maxima, as the usual dust traps, but by a difference in precession rates between the gas and dust. Indeed, this difference makes the radial drift inefficient in two locations, leading to the formation of two dust rings whose position depends on the system parameters. This phenomenon is likely to occur to marginally coupled dust particles $(\text{St}\gtrsim1)$ as both the effect of gravitational and drag force are considerable. We then perform a suite of three-dimensional SPH numerical simulations to compare the results with our theoretical predictions. We explore the parameter space, varying stellar mass ratio, disc thickness, radial extension, and we find a general agreement with the analytical expectations. Such dust pile-up prevents radial drift, fosters dust growth and may thus promote the planet formation in circumbinary discs.