FAUST XXX: Dust enhancement in the young binary L1551 IRS 5

TL;DR

This paper presents ALMA observations and hydrodynamical models of the circumbinary disc around young binary L1551 IRS 5, revealing dust over-densities likely caused by binary interactions, indicating early planet formation processes.

Contribution

The study combines high-resolution ALMA data with 3D hydrodynamical simulations to analyze dust over-densities in a young binary's circumbinary disc, providing new insights into early planet formation.

Findings

Detection of asymmetric dust over-densities in the circumbinary disc.

Hydrodynamical models support binary-disc interactions as the cause.

Potential sites for early planet formation identified.

Abstract

Young binary stars with discs provide unique laboratories to study the earliest stages of planet formation in star-forming environments. The detection of substructure in discs around Class I protostars challenges current models of disc evolution, suggesting that planets may form earlier than previously expected ($<1$ Myr). In the context of the ALMA Large Program FAUST, we present observations of the circumbinary disc (CBD) around the young binary system L1551 IRS 5. The CBD exhibits two prominent over-densities in the continuum emission at the edge of the cavity, with the Northern over-density being about 20% brighter than the Southern one. By analysing the disc morphology and kinematics of L1551 IRS 5, we delineate dynamical constraints on the binary's orbital parameters. Additionally, we present 3D hydrodynamical models of the CBD to predict both the dust and the gas surface densities. Then, we compare the resulting synthetic observations with ALMA observations of the continuum emission at 1.3 mm and the C$^{18}$O line emission. Our analysis suggests that the density enhancements observed with ALMA in L1551 IRS 5 can be caused by interactions between the binary stars and the CBD, leading to dust concentration within the disc. We conclude that the observed over-density corresponds to a location where could potentially grow under favourable conditions.