Discs are born off-center

Benoît Commerçon1,? , Francesco Lovascio1, Elliot Lynch1, and Enrico Ragusa2,3
1 University of Lyon, University of Lyon 1, École Normale Supérieure de Lyon, CNRS, Lyon Astrophysics Research Center UMR5574, F-69230 Saint-Genis-Laval,
France
2 Department of Mathematics, University of Milan, Via Saldini 50, 20133 Milan, Italy
3 Department of Physics, University of Milan, Via Celoria 16, 20133 Milan MI, Italy
Received February 14, 2024 / Accepted August 16, 2024

ABSTRACT
Context. Recent observations have begun probing the early phases of disc formation, but little data yet exists on disc structure and morphology of Class 0 objects. Using simulations, we are able to lay out predictions of disc morphologies expected in future surveys of young discs. Based on detailed simulations of ab initio star formation by core collapse, we predict that early discs must be eccentric.

Aims. In this Letter, we study the morphology and, in particular, the eccentricity of discs formed in non-ideal magnetohydrodynamic (MHD) collapse simulations. We attempt to show that discs formed by cloud collapse are likely to be eccentric. Methods. We ran non-ideal MHD collapse simulations in the adaptive mesh refinement code RAMSES with radiative transfer. We used state-of-the-art analysis methods to measure the disc eccentricity. Results. We find that despite no asymmetry in the initial conditions, the discs formed are eccentric, with eccentricities on the order of 0.1. Conclusions. These results may have important implications for protoplanetary disc dynamics and planet formation. The presence of eccentricity in young discs that is not seen at later stages of disc evolution is at odds with current viscous eccentricity damping models. This implies that there may be an as-yet undiscovered circularization mechanism in circumstellar discs.

https://www.aanda.org/articles/aa/pdf/2024/09/aa49610-24.pdf