Observational constraints on gas disc sizes in the protoplanetary discs of multiple systems in the Taurus region

¹ Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy
e-mail: alessiaannie.rota@studenti.unimi.it
² European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
e-mail: cmanara@eso.org
³ Kavli Institute for Astronomy and Astrophysics, Peking University, Yiheyuan 5, Haidian Qu, 100871 Beijing, PR China
⁴ Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
⁵ Institute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA Cambridge, UK
⁶ Observatoire de Paris, PSL University, Sorbonne University, CNRS, LERMA, 61 Av. de l’Observatoire, 75014 Paris, France
⁷ Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astro-Math Bldg, 1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan
⁸ Institute of Astronomy, Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
⁹ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹⁰ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹¹ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
¹² School of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
¹³ Univ Lyon, Univ Lyon1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, 69230 Saint-Genis-Laval, France

Received: 9 April 2021
Accepted: 22 December 2021

Abstract

The formation of multiple stellar systems is a natural by-product of the star-formation process, and its impact on the properties of protoplanetary discs and on the formation of planets is not yet fully understood. To date, no detailed uniform study of the gas emission from a sample of protoplanetary discs around multiple stellar systems has been performed. Here we analyse new ALMA observations of the molecular CO gas emission at a ~21 au resolution, specifically targeting discs in eight multiple stellar systems in the Taurus star-forming regions. ¹²CO gas emission is detected around all primaries and in seven companions. With these data, we estimate the inclination and the position angle (PA) for all primary discs and for five secondary or tertiary discs, and measure the gas disc radii of these objects with a cumulative flux technique on the spatially resolved zeroth moment images. When considering the radius, including 95% of the flux as a metric, the estimated size of the gas disc in multiple stellar systems is found to be on average ~4.2 times larger than the size of the dust disc. This ratio is higher than what was recently found in a population of more isolated and single systems. On the contrary, when considering the radius including 68% of the flux, no difference between multiple and single discs is found in the distribution of ratios. This discrepancy is due to the sharp truncation of the outer dusty disc observed in multiple stellar systems. The measured sizes of gas discs are consistent with tidal truncation models in multiple stellar systems assuming eccentricities of ~0.15–0.5, as expected in typical binary systems.