Zoom-Simulations of Protoplanetary Disks starting from GMC scales

TL;DR

This study uses high-resolution simulations to explore the complex, heterogeneous processes of protoplanetary disk formation around massive stars within giant molecular clouds, highlighting the roles of turbulence and magnetic fields.

Contribution

It provides the first detailed, multi-scale simulation of disk formation from GMC scales, demonstrating the robustness of disk formation and the importance of turbulence and magnetic transport.

Findings

Accretion rates vary widely over time and among stars.

Disk formation is robust despite varying numerical parameters.

Magnetic transport balances inward mechanical angular momentum transport.

Abstract

We investigate the formation of protoplanetary disks around nine solar mass stars formed in the context of a (40 pc)$^3$ Giant Molecular Cloud model, using RAMSES adaptive-mesh refinement simulations extending over a scale range of about 4 million, from an outer scale of 40 pc down to cell sizes of 2 AU. Our most important result is that the accretion process is heterogeneous in multiple ways; in time, in space, and among protostars of otherwise similar mass. Accretion is heterogeneous in time, in the sense that accretion rates vary during the evolution, with generally decreasing profiles, whose slopes vary over a wide range, and where accretion can increase again if a protostar enters a region with increased density and low speed. Accretion is heterogeneous in space, because of the mass distribution, with mass approaching the accreting star-disk system in filaments and sheets. Finally, accretion is heterogeneous among stars, since the detailed conditions and dynamics in the neighborhood of each star can vary widely. We also investigate the sensitivity of disk formation to physical conditions, and test their robustness by varying numerical parameters. We find that disk formation is robust even when choosing the least favorable sink particle parameters, and that turbulence cascading from larger scales is a decisive factor in disk formation. We also investigate the transport of angular momentum, finding that the net inward mechanical transport is compensated for mainly by an outward directed magnetic transport, with a contribution from gravitational torques usually subordinate to the magnetic transport.