Conditions for Circumstellar Disk Formation: Effects of Initial Conditions and Sink Treatment

TL;DR

This study uses 3D magnetohydrodynamic simulations to explore how initial cloud conditions and sink treatment influence circumstellar disk formation, revealing sensitivity to density profiles, sink parameters, and magnetic effects.

Contribution

It demonstrates that initial cloud density profiles and sink treatment critically affect disk size and formation, highlighting the importance of these factors in simulations.

Findings

Disk size varies significantly with initial density profile.

Large sinks hinder disk formation and affect outflow properties.

Proper sink parameters are essential for accurate disk formation modeling.

Abstract

The formation of a circumstellar disk in collapsing cloud cores is investigated with three-dimensional magnetohydrodynamic simulations. We prepare four types of initial cloud having different density profiles and calculate their evolution with or without a sink. To investigate the effect of magnetic dissipation on disk formation, the Ohmic dissipation is considered in some models. Calculations show that disk formation is very sensitive to both the initial cloud configuration and the sink treatment. The disk size considerably differs in clouds with different density profiles even when the initial clouds have almost the same mass-to-flux ratio. Only a very small disk (\sim 10 AU in size) appears in clouds with a uniform density profile, whereas a large disk (\sim 100 AU in size) forms in clouds with a Bonnor-Ebert density profile. In addition, a large sink accretion radius numerically impedes disk formation during the main accretion phase and tends to foster the misleading notion that disk formation is completely suppressed by magnetic braking. The protostellar outflow is also greatly affected by the sink properties. A sink accretion radius of \lesssim 1 AU and sink threshold density of \gtrsim 10^ 13 cm^-3 are necessary for investigating disk formation during the main accretion phase.