Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Protostellar Core Formation

TL;DR

This study presents the first 3D radiation magnetohydrodynamic simulations of protostellar collapse, capturing early star formation phases with detailed physics, including Ohmic dissipation, and revealing insights into core formation, disk development, and outflows.

Contribution

It introduces comprehensive 3D RMHD simulations of protostellar collapse with realistic physics and no sink particles, advancing understanding of early star formation processes.

Findings

Protostellar cores form with structures consistent with 1D models.

Ohmic dissipation enables circumstellar disk formation near cores.

Magnetic fields launch outflows from both first and protostellar cores.

Abstract

We report the first three-dimensional radiation magnetohydrodynamic (RMHD) simulations of protostellar collapse with and without Ohmic dissipation.We take into account many physical processes required to study star formation processes, including a realistic equation of state. We follow the evolution from molecular cloud cores until protostellar cores are formed with sufficiently high resolutions without introducing a sink particle. The physical processes involved in the simulations and adopted numerical methods are described in detail.We can calculate only about one year after the formation of the protostellar cores with our direct three-dimensional RMHD simulations because of the extremely short timescale in the deep interior of the formed protostellar cores, but successfully describe the early phase of star formation processes. The thermal evolution and the structure of the first and second (protostellar) cores are consistent with previous one-dimensional simulations using full radiation transfer, but differ considerably from preceding multi-dimensional studies with the barotropic approximation. The protostellar cores evolve virtually spherically symmetric in the ideal MHD models because of efficient angular momentum transport by magnetic fields, but Ohmic dissipation enables the formation of the circumstellar disks in the vicinity of the protostellar cores as in previous MHD studies with the barotropic approximation. The formed disks are still small (less than 0.35 AU) because we simulate only the earliest evolution. We also confirm that two different types of outflows are naturally launched by magnetic fields from the first cores and protostellar cores in the resistive MHD models.