Star Formation in Relic HII Regions of the First Stars: Binarity and Outflow Driving

Abstract

Star formation in relic HII regions of the first stars is investigated using magneto-hydrodynamical simulations with a nested grid method that covers 10 orders of magnitude in spatial scale and 20 orders of magnitude in density contrast. Due to larger fraction of H_2 and HD molecules, its prestellar thermal evolution is considerably different from that in the first star formation. Reflecting the difference, two hydrostatic cores appear in a nested manner: a protostar is enclosed by a transient hydrostatic core, which appears during the prestellar collapse. If the initial natal core rotates fast at a rate with rotational to gravitational energy ratio β_0 > 0.01-0.1, the transient hydrostatic core fragments to \sim 10 M_\odot sub-cores at density \sim 10^9 cm^-3. With smaller rotation energy, fragmentation occurs at higher density while a single protostar forms without fragmentation if rotation is extremely slow with β_0 < 10^-6 -10^-5. If magnetic field is present, these threshold values of β_0 is boosted owing to angular momentum transport by the magnetic breaking. Magnetic field also drives the protostellar outflows. With strong magnetic field, two distinct outflows are observed: The slower one emanates from the transient hydrostatic core, while the faster one from the protostar. These flows may affect the final stellar mass by ejecting some of masses in the initial core, and also may play some role in driving and maintenance of interstellar turbulence in young galaxies.

11 pages, 2 figures. Accepted for publication in ApJ. For high resolution figures, see http://www2-tap.scphys.kyoto-u.ac.jp/~machidam/astro-ph/RelicHIIregion.pdf

References in corpus (17)

• Thermal and Fragmentation Properties of Star-forming Clouds in Low-metallicity Environments
• Protostar Formation in the Early Universe
• The Formation of Population III Binaries from Cosmological Initial Conditions
• The First Cosmic Structures and their Effects
• The First Galaxies: Assembly, Cooling and the Onset of Turbulence
• Resolving the Formation of Protogalaxies. I. Virialization
• Cosmological Magnetic Field: a fossil of density perturbations in the early universe
• Collapse and Fragmentation of Rotating Magnetized Clouds. I. Magnetic Flux - Spin Relation
• The Biermann Battery in Cosmological MHD Simulations of Population III Star Formation
• Formation of Massive Primordial Stars in a Reionized Gas
• Formation of Population III Stars in Fossil HII Regions: Significance of HD
• Conditions for the Formation of First-Star Binaries
• The Impact of HD Cooling on the Formation of the First Stars
• Magneto-Hydrodynamics of Population III Star Formation
• The First Jet in the Universe: Protostellar Jets from the First Stars
• The role of HD cooling in primordial star formation
• First Stars III Conference Summary

Cited by in corpus (6)

• The Formation of Population III Stars in Gas Accretion Stage: Effects of Magnetic Fields
• Protostellar Feedback and Final Mass of the Second-Generation Primordial Stars
• Accretion Phase of Star Formation in Clouds with Different Metallicities
• Do the environmental conditions affect the dust-induced fragmentation in low-metallicity clouds ?: Effect of pre-ionization and far-ultraviolet/cosmic-ray fields
• Evolution of Magnetic Fields in Collapsing Star-forming Clouds under Different Environments
• Driving Conditions of Protostellar Outflows in Different Star-Forming Environments