Growth of Massive Disk and Early Disk Fragmentation in the Primordial Star Formation

Abstract

Recent high-resolution simulations demonstrate that disks around primordial protostars easily fragment in the accretion phase before the protostars accrete less than a solar mass. To understand why the gravitational instability generally causes the fragmentation so early, we develop a one-dimensional (1D) non-steady model of the circumstellar disk that takes the mass supply from an accretion envelope into account. We also compare the model results to a three-dimensional (3D) numerical simulation performed with a code employing the adaptive mesh refinement. Our model shows that the self-gravitating disk, through which the Toomre $Q$ parameter is nearly constant at $Q\sim 1$, gradually spreads as the disk is fed by the gas infalling from the envelope. We further find that the accretion rate onto the star is an order of magnitude smaller than the mass supply rate onto the disk. This discrepancy makes the disk more massive than the protostar in an early evolutionary stage. Most of the infalling gas is used to extend the outer part of the self-gravitating disk rather than transferred inward toward the star through the disk. We find that similar evolution also occurs in the 3D simulation, where the disk becomes three times more massive than the star before the first fragmentation occurs. Our 1D disk model well explains the evolution of the disk-to-star mass ratio observed in the simulation. We argue that the formation of such a massive disk leads to the early disk fragmentation.

22 pages, 14 figures, accepted for publication in ApJ

References in corpus (22)

• Radiation-Hydrodynamic Simulations of Collapse and Fragmentation in Massive Protostellar Cores
• The Formation of Population III Binaries from Cosmological Initial Conditions
• Primordial Star Formation under the Influence of Far Ultraviolet Radiation: 1540 Cosmological Halos and the Stellar Mass Distribution
• The Mass Spectrum of the First Stars
• The Formation of the First Stars II. Radiative Feedback Processes and Implications for the Initial Mass Function
• A Triple Protostar System Formed via Fragmentation of a Gravitationally Unstable Disk
• The Thermal Regulation of Gravitational Instabilities in Protoplanetary Disks III. Simulations with Radiative Cooling and Realistic Opacities
• Formation of massive protostars in atomic cooling haloes
• Formation of Massive Primordial Stars in a Reionized Gas
• Formation of primordial supermassive stars by burst accretion
• Merge or survive: Number of Population III stars per minihalo
• Does disk fragmentation prevent the formation of supermassive stars in protogalaxies?
• Radiation hydrodynamics simulations of the formation of direct-collapse supermassive stellar systems
• Conditions for the Formation of First-Star Binaries
• Effects of radiation transfer on the structure of self-gravitating disks, their fragmentation and evolution of the fragments
• Spiral arms and instability within the AFGL 4176 mm1 disc
• Dynamical evolution of Population III stellar systems and the resulting binary statistics
• Spiral-arm instability: giant clump formation via fragmentation of a galactic spiral arm
• Fragmentation inside atomic cooling haloes exposed to Lyman-Werner radiation
• Gravitational stability and fragmentation condition for discs around accreting supermassive stars
• Disk fragmentation and intermittent accretion onto supermassive stars
• Primordial protostars accreting beyond the $\Omega \Gamma$-limit: radiation effect around the star-disk boundary

Cited by in corpus (9)

• Formation and evolution of protostellar accretion discs. II. From 3D simulation to a simple semi-analytic model of Class 0/I discs
• Formation of Massive and Wide First-star Binaries in Radiation Hydrodynamics Simulations
• Population III star formation in an X-ray background: III. Periodic radiative feedback and luminosity induced by elliptical orbits
• Intermediate-mass Black Holes on the Run from Young Star Clusters
• 3D Radiation-Hydrodynamic Simulations Resolving Interior of Rapidly Accreting Primordial Protostar
• Non-ideal magnetohydrodynamic simulations of the first star formation: the effect of ambipolar diffusion
• Protostellar-disc fragmentation across all metallicities
• Population III Star Formation in an X-ray background: II. Protostellar Discs, Multiplicity and Mass Function of the Stars
• Population III Star Formation in an X-ray background: I. Critical Halo Mass of Formation and Total Mass in Stars