Impact of magnetic fields on Population III star formation

Abstract

The theory of the formation of the first stars in the Universe, the so-called Population III (Pop III), has until now largely neglected the impact of magnetic fields. Complementing a series of recent studies of the magneto-hydrodynamic (MHD) aspects of Pop III star formation, we here carry out a suite of idealized numerical experiments where we ascertain how the fragmentation properties of primordial protostellar discs are modified if MHD effects are present. Specifically, starting from cosmological initial conditions, we focus on the central region in a select minihalo at redshift $z\sim$ 25, inserting a magnetic field at an intermediate evolutionary stage, normalized to a fraction of the equipartition value. To explore parameter space, we consider different field geometries, including uniform, radial, toroidal, and poloidal field configurations, with the toroidal configuration being the most realistic. The collapse of the gas is followed for $\sim$8 orders of magnitude in density after the field was inserted, until a maximum of $10^{15}{\mathrm{cm}}^{-3}$ is reached. We find that the magnetic field leads to a delay in the collapse of the gas. Moreover, the toroidal field has the strongest effect on the collapse as it inhibits the fragmentation of the emerging disc surrounding the central core and leads to the formation of a more massive core. The full understanding of the formation of Pop~III stars and their mass distribution thus needs to take into account the effect of magnetic fields. We further conclude that ideal MHD is only a first step in this endeavor, to be followed-up with a comprehensive treatment of dissipative effects, such as ambipolar diffusion and Ohmic dissipation.

Accepted by MNRAS

References in corpus (19)

• Theory of Star Formation
• Protostar Formation in the Early Universe
• The Formation of Population III Binaries from Cosmological Initial Conditions
• Grackle: a Chemistry and Cooling Library for Astrophysics
• A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence
• Population III star formation in a Lambda CDM universe, I: The effect of formation redshift and environment on protostellar accretion rate
• The Birth of a Galaxy. II. The Role of Radiation Pressure
• Magnetohydrodynamic Simulations of Disk Galaxy Formation: the Magnetization of The Cold and Warm Medium
• The Biermann Battery in Cosmological MHD Simulations of Population III Star Formation
• Constraining the primordial initial mass function with stellar archaeology
• The Turbulent Dynamo in Highly Compressible Supersonic Plasmas
• Star Formation in the First Galaxies I: Collapse Delayed by Lyman-Werner Radiation
• Magneto-Hydrodynamics of Population III Star Formation
• The influence of magnetic fields on the thermodynamics of primordial star formation
• Magnetic Fields in the Formation of the First Stars. I. Theory vs. Simulation
• Magnetic fields in the formation of the first stars.--II Results
• Ionization degree and magnetic diffusivity in the primordial star-forming clouds
• First Star Formation in the Presence of Primordial Magnetic Fields
• Amplification of Magnetic Fields in a Primordial HII Region and Supernova

Cited by in corpus (1)

• From dark matter halos to pre-stellar cores: High resolution follow-up of cosmological Lyman-Werner simulations