Cosmic-ray ionization rate versus Dust fraction: Which plays a crucial role in the early evolution of the circumstellar disk?

Abstract

We study the formation and early evolution of young stellar objects (YSOs) using three-dimensional non-ideal magnetohydrodynamic (MHD) simulations to investigate the effect of cosmic ray ionization rate and dust fraction (or amount of dust grains) on circumstellar disk formation. Our simulations show that a higher cosmic ray ionization rate and a lower dust fraction lead to (i) a smaller magnetic resistivity of ambipolar diffusion, (ii) a smaller disk size and mass, and (iii) an earlier timing of outflow formation and a greater angular momentum of the outflow. In particular, at a high cosmic ray ionization rate, the disks formed early in the simulation are dispersed by magnetic braking on a time scale of about 104 years. Our results suggest that the cosmic ray ionization rate has a particularly large impact on the formation and evolution of disks, while the impact of the dust fraction is not significant.

8 pages, 10 figures, accepted for publication in MNRAS

References in corpus (8)

• Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations
• Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Non-Ideal Magnetohydrodynamic Effects and Early Formation of Circumstellar Disks
• Effects of Ohmic and ambipolar diffusion on the formation and evolution of the first cores, protostars and circumstellar discs
• Decoupling of Magnetic Fields in Collapsing Protostellar Envelopes and Disk Formation and Fragmentation
• "Ash-fall" induced by molecular outflow in protostar evolution
• The impact of non-ideal magnetohydrodynamic processes on discs, outflows, counter-rotation and magnetic walls during the early stages of star formation
• Ionization: a possible explanation for the difference of mean disk sizes in star-forming regions
• Early evolution of disk, outflow, and magnetic field of young stellar objects: Impact of dust model

Cited by in corpus (1)

• Co-evolution of dust grains and protoplanetary disks II: structure and evolution of protoplanetary disks; an analytical approach