On dust evolution in planet-forming discs in binary systems – II. Comparison with Taurus and ρ Ophiuchus (sub-)millimetre observations: discs in binaries have small dust sizes

Monthly Notices of the Royal Astronomical Society, vol. 507, pp. 2531–2549

Abstract

ABSTRACT The recently discovered exoplanets in binary or higher order multiple stellar systems sparked a new interest in the study of protoplanetary discs in stellar aggregations. Here, we focus on disc solids, as they make up the reservoir out of which exoplanets are assembled and dominate (sub-)millimetre disc observations. These observations suggest that discs in binary systems are fainter and smaller than in isolated systems. In addition, disc dust sizes are consistent with tidal truncation only if they orbit very eccentric binaries. In a previous study, we showed that the presence of a stellar companion hastens the radial migration of solids, shortening disc lifetime, and challenging planet formation. In this paper, we confront our theoretical and numerical results with observations: Disc dust fluxes and sizes from our models are computed at ALMA wavelengths and compared with Taurus and ρ Ophiuchus data. A general agreement between theory and observations is found. In particular, we show that the dust disc sizes are generally smaller than the binary truncation radius due to the combined effect of grain growth and radial drift: Therefore, small disc sizes do not require implausibly high eccentricities to be explained. Furthermore, the observed binary discs are compatible within 1σ with a quadratic flux–radius correlation similar to that found for single-star discs and show a close match with the models. However, the observational sample of resolved binary discs is still small and additional data are required to draw more robust conclusions on the flux–radius correlation and how it depends on the binary properties.

Authors 3

1. Francesco Zagaria corresponding Aachen Leiden Observatory

   Leiden University · University of Cambridge · University of Pavia · Leiden Observatory · Istituto Universitario di Studi Superiori di Pavia

   Affiliation as printed

   Dipartimento di Fisica, Università degli Studi di Pavia, Via Agostino Bassi 6, I-27100 Pavia, Italy

   Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

   Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, the Netherlands

   Scuola Universitaria Superiore IUSS Pavia, Piazza della Vittoria 15, I-27100 Pavia, Italy

2. Giovanni P. Rosotti Aachen Leiden Observatory

   Leiden University · University of Leicester · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, the Netherlands

   School of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK

3. Giuseppe Lodato

   University of Milan

   Affiliation as printed

   Dipartimento di Fisica, Università degli Studi di Milano, Via Giovanni Celoria 16, I-20133 Milano, Italy