Disc fragmentation and oligarchic growth of protostellar systems in low-metallicity gas clouds

Abstract

We study low-metallicity star formation with a set of high-resolution hydrodynamics simulations for various gas metallicities over a wide range $0$--$10^{-3}{\mathrm{Z}}_{⨀}$. Our simulations follow non-equilibrium chemistry and radiative cooling by adopting realistic elemental abundance and dust size distribution. We examine the condition for the fragmentation of collapsing clouds (cloud fragmentation; CF) and of accretion discs (disc fragmentation; DF). We find that CF is suppressed due to rapid gas heating accompanied with molecular hydrogen formation even with efficient dust cooling for metallicities $\gtrsim 10^{-5}{\mathrm{Z}}_{⨀}$. Instead, DF occurs in almost all runs regardless of metallicity. We also find that, in the accretion discs, the growth of the protostellar systems is overall oligarchic. The primary protostar grows through the accretion of gas, and secondary protostars form through the interaction of spiral arms or the break-up of a rapidly rotating protostar. Despite vigorous fragmentation, a large fraction of secondary protostars are destroyed through mergers or tidal disruption events. For a few hundred years after the first adiabatic core formation, only several protostars survive in the disc, and the total mass of protostars is $0.52$--$3.8{\mathrm{M}}_{⨀}$.

29 pages, 24 figures, 4 tables, accepted for publication in MNRAS

References in corpus (20)

• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• Dust Formation and Survival in Supernova Ejecta
• Grackle: a Chemistry and Cooling Library for Astrophysics
• The Mass Spectrum of the First Stars
• The Destruction of Cosmological Minihalos by Primordial Supernovae
• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• The Birth of a Massive First-Star Binary
• Formation sites of Population III star formation: The effects of different levels of rotation and turbulence on the fragmentation behavior of primordial gas
• Merge or survive: Number of Population III stars per minihalo
• Dust-cooling--induced Fragmentation of Low-metallicity Clouds
• Supernova dust formation and the grain growth in the early universe: The critical metallicity for low-mass star formation
• Accretion Phase of Star Formation in Clouds with Different Metallicities
• Spiral-arm instability: giant clump formation via fragmentation of a galactic spiral arm
• Formation of massive stars under protostellar radiation feedback: Very metal-poor stars
• Physical Mechanism for the Intermediate Characteristic Stellar Mass in the Extremely Metal-poor Environments
• Particle splitting in smoothed particle hydrodynamics based on Voronoi diagram
• Seeding the second star -- II. CEMP star formation enriched from faint supernovae
• Amplification of turbulence in contracting prestellar cores in primordial minihalos
• Spiral arm instability -- III. Fragmentation of primordial protostellar discs
• Fragmentation in a Primordial Accretion Flow

Cited by in corpus (5)

• Dynamical evolution of Population III stellar systems and the resulting binary statistics
• Gravitational waves from the remnants of the first stars in nuclear star clusters
• Gravitational Fragmentation of Extremely Metal-poor Circumstellar Discs
• Coronal Properties of Low-mass Population III Stars and the Radiative Feedback in the Early Universe
• When did the initial mass function become bottom-heavy?