Sculpting protoplanetary discs -- modelling circumbinary cavities at observable scales with radiation hydrodynamics

TL;DR

This study uses radiation hydrodynamics simulations to explore how radiative cooling influences the shape and size of cavities in circumbinary discs, revealing that cooling timescales are key to cavity morphology.

Contribution

The paper introduces a comprehensive set of 2D radiation hydrodynamics simulations that demonstrate the impact of radiative cooling on circumbinary cavity structures, unifying observations with a physical model.

Findings

Cavity shapes vary with radiative cooling timescales.

Discs with cooling timescales similar to orbital periods produce more circular cavities.

The model explains cavity structures in systems like Cs Cha and GG Tau.

Abstract

Observations of circumbinary discs reveal inner cavities, with their shape and size varying strongly between different systems. The structure of the cavity is determined by the complex interplay between spirals induced by tidal forcing from the binary and the viscous and radiative damping of the spirals at the cavity edge. To fully understand what determines the properties of observed cavities, it is therefore necessary to capture the effect of radiative processes in modelling. To this end, we run 27 simulations of circumbinary discs in 2D using the PLUTO code. These simulations include various size scales, binary eccentricities and thermodynamic models. We find that the diverse cavity shapes are a natural outcome of the radially-varying cooling timescale, as different radiative processes mediate cooling at different disc size regimes. For binaries with separation of a few au, where the cooling timescale is comparable to the orbital timescale at the cavity edge, we recover much more circular cavities than for quickly- or slowly-cooling discs. Our results show that the cavity structure around several binary systems such as Cs Cha and GG Tau can be explained with one physical model, and highlight the importance of radiative cooling in modelling the dynamical evolution of circumbinary discs.