Simulations of the isothermal collapse of magnetic rotating protostellar clouds

TL;DR

This study uses 2D MHD simulations to explore the hierarchical structure formation during the isothermal collapse of magnetic protostellar clouds, revealing the formation of primary disks and their properties.

Contribution

It provides new insights into the formation and characteristics of primary disks in collapsing magnetic protostellar clouds through detailed numerical simulations.

Findings

Protostellar clouds develop a hierarchical structure by the end of collapse.

Primary disks form when magnetic energy exceeds 20% of gravitational energy.

Primary disks contain 30-80% of the initial cloud mass.

Abstract

We investigate collapse of magnetic protostellar clouds of mass $10$ and $1 M_{\odot}$. The collapse is simulated numerically using the two-dimensional magnetohydrodynamic (MHD) code `Enlil'. The simulations show that protostellar clouds acquire a hierarchical structure by the end of the isothermal stage of collapse. Under the action of the electromagnetic force, the protostellar cloud takes the form of an oblate envelope with the half-thickness to radius ratio $Z/R \sim (0.20-0.95)$. A geometrically and optically thin primary disk with radius $0.2-0.7 R_0$ and $Z/R \sim (10^{-2}-10^{-1})$ forms inside the envelope, where $R_0$ is the initial radius of the cloud. Primary disks are the structures in magnetostatic equilibrium. They form when the initial magnetic energy of the cloud exceeds $20 \%$ of its gravitational energy. The mass of the primary disk is $30-80 \%$ of the initial mass of the cloud. The first hydrostatic core subsequently forms in the center of the primary disc. We discuss the role of primary disks in the further evolution of clouds, as well as possible observational appearance of the internal hierarchy of the collapsing cloud from the point of view of the features of the magnetic field geometry and the distribution of angular momentum at different levels of the hierarchy