# The First Two Thousand Years of Star Formation

## TL;DR

This study uses advanced 3D resistive magnetohydrodynamic simulations to explore the early evolution of star formation, including disk formation, magnetic effects, episodic accretion, and jet/outflow phenomena over the first two thousand years.

## Contribution

It provides detailed simulation results of the first two thousand years of star formation, highlighting magnetic dissipation, gravitational instability, and episodic jet activity.

## Key findings

- Formation of a small, persistent protostellar disk.
- Development of episodic mass accretion and high-velocity jets.
- Presence of outflows with knots and cavity structures similar to observations.

## Abstract

Starting from a prestellar core with a size of $1.2\times10^4$ AU, we calculate the evolution of a gravitationally collapsing core until $\sim2000$ yr after protostar formation using a three-dimensional resistive magnetohydrodynamic simulation, in which the protostar is resolved with a spatial resolution of $5.6\times10^{-3}$ AU. Following protostar formation, a rotationally supported disk is formed. Although the disk size is as small as $\sim2-4$ AU, it remains present until the end of the simulation. Since the magnetic field dissipates and the angular momentum is then not effectively transferred by magnetic effects, the disk surface density gradually increases and spiral arms develop due to gravitational instability. The disk angular momentum is then transferred mainly by gravitational torques, which induce an episodic mass accretion onto the central protostar. The episodic accretion causes a highly time-variable mass ejection (the high-velocity jet) near the disk inner edge, where the magnetic field is well coupled with the neutral gas. As the mass of the central protostar increases, the jet velocity gradually increases and exceeds $\sim100$ km s$^{-1}$. The jet opening angle widens with time at its base, while the jet keeps a very good collimation on the large scale. In addition, a low-velocity outflow is driven from the disk outer edge. A cavity-like structure, a bow shock and several knots, all of which are usually observed in star-forming regions, are produced in the outflowing region.