Zooming in on the Formation of Protoplanetary Disks

TL;DR

This study models protoplanetary disk formation using high-resolution simulations, revealing universal scaling laws, magnetic braking effects, and outflow characteristics in realistic star formation environments.

Contribution

It provides the first detailed, multi-scale simulation of disk formation incorporating magnetic fields and outflows in realistic conditions.

Findings

Accretion rate peaks at 6 kyr then decays exponentially.

Magnetic fields enable efficient accretion and disk growth.

Magnetic field strength varies from >10 G to <1 mG across scales.

Abstract

We use the adaptive mesh refinement code RAMSES to model the formation of protoplanetary disks in realistic star formation environments. The resolution scales over up to 29 powers of two ($\sim$ 9 orders of magnitude) covering a range from outer scales of 40 pc to inner scales of 0.015 AU. The accretion rate from a 1.5 solar mass envelope peaks near $10^{-4}$ $\mspy$ about 6 kyr after sink particle formation and then decays approximately exponentially, reaching $10^{-6}$ $\mspy$ in 100 kyr. The models suggest universal scalings of physical properties with radius during the main accretion phase, with kinetic and / or magnetic energy in approximate balance with gravitational energy. Efficient accretion is made possible by the braking action of the magnetic field, which nevertheless allows a near-Keplerian disk to grow to a 100 AU size. The magnetic field strength ranges from more than 10 G at 0.1 AU to less than 1 mG at 100 AU, and drives a time dependent bipolar outflow, with a collimated jet and a broader disk wind.