Gravitational stability and fragmentation condition for discs around accreting supermassive stars

Abstract

Supermassive stars (SMSs) with mass $\sim 10^5{\mathrm{M}}_{\odot }$ are promising candidates for the origin of supermassive black holes observed at redshift $\gtrsim 6$. They are supposed to form as a result of rapid accretion of primordial gas, although it can be obstructed by the time variation caused by circum-stellar disc fragmentation due to gravitational instability. To assess the occurrence of fragmentation, we study the structure of marginally gravitationally unstable accretion discs, by using a steady one-dimensional thin disc model with detailed treatment of chemical and thermal processes. Motivated by two SMS formation scenarios, i.e., those with strong ultraviolet radiation background or with large velocity difference between the baryon and the dark matter, we consider two types of flows, i.e., atomic and molecular flows, respectively, for a wide range of the central stellar mass $10-10^5{\mathrm{M}}_{\odot }$ and the accretion rate $10^{-3}-1{\mathrm{M}}_{\odot }{\mathrm{yr}}^{-1}$. In the case of a mostly atomic gas flowing to the disc outer boundary, the fragmentation condition is expressed as the accretion rate being higher than the critical value of $10^{-1}{\mathrm{M}}_{\odot }{\mathrm{yr}}^{-1}$ regardless of the central stellar mass. On the other hand, in the case of molecular flows, there is a critical disc radius outside of which the disc becomes unstable. Those conditions appears to be marginally satisfied according to numerical simulations, suggesting that disc fragmentation can be common during SMS formation.

17 pages, 10 figures, accepted for publication in MNRAS

References in corpus (17)

• Can Supermassive Black Holes Form in Metal-Enriched High-Redshift Protogalaxies ?
• The Evolution of Supermassive Population III Stars
• The critical radiation intensity for direct collapse black hole formation: dependence on the radiation spectral shape
• Accretion onto Intermediate-Mass Black Holes in Dense Protogalactic Clouds
• Supersonic Gas Streams Enhance the Formation of Massive Black Holes in the Early Universe
• Formation of massive protostars in atomic cooling haloes
• The Final Fates of Accreting Supermassive Stars
• Formation of an embryonic supermassive star in the first galaxy
• The formation of direct collapse black holes under the influence of streaming velocities
• Formation of primordial supermassive stars by burst accretion
• The Direct Collapse of a Massive Black Hole Seed Under the Influence of an Anisotropic Lyman-Werner Source
• Does disk fragmentation prevent the formation of supermassive stars in protogalaxies?
• Radiation hydrodynamics simulations of the formation of direct-collapse supermassive stellar systems
• Spin-orbit Misalignment as a Driver of the Kepler Dichotomy
• Effects of radiation transfer on the structure of self-gravitating disks, their fragmentation and evolution of the fragments
• Self-regulated gravitational accretion in protostellar discs
• Upper stellar mass limit by radiative feedback at low-metallicities: metallicity and accretion rate dependence

Cited by in corpus (7)

• Light, medium-weight or heavy? The nature of the first supermassive black hole seeds
• Formation of supermassive stars in the first star clusters
• Thermal evolution of protoplanetary disks: from $\beta$-cooling to decoupled gas and dust temperatures
• Growth of Massive Disk and Early Disk Fragmentation in the Primordial Star Formation
• Isotopic and vibrational-level dependence of H${}_2$ dissociation by electron impact
• Disk fragmentation and intermittent accretion onto supermassive stars
• Population III Star Formation in an X-ray background: II. Protostellar Discs, Multiplicity and Mass Function of the Stars