Intermittent fragmentation and statistical variations during gas collapse in magnetised atomic cooling haloes

Abstract

Observations reveal the presence of supermassive black holes (SMBH) as early as ~700 million years after the Big Bang. Their formation path is still subject to current debate. We explore the influence of magnetic fields, which are strongly amplified via the turbulent small-scale dynamo, on the formation of SMBH seeds within the direct collapse scenario. In this study, we perform for the first time cosmological magnetohydrodynamic large eddy simulations that employ a model for unresolved, compressible MHD turbulence. In total we perform 36 simulations for 9 haloes each with two different initial magnetic field strengths, and with and without employing the unresolved turbulence model. We make use of the adaptive mesh refinement approach to achieve an effective spatial resolution of less than one proper astronomical unit. We consider a regime where cooling is regulated by atomic hydrogen and the molecular hydrogen gets dissociated by a strong radiation field. Our main finding is that the majority of the gas properties in the haloes at the final output are predominantly determined by the run-away gravitational collapse. Turbulence is supersonic and super-Alfvénic in all cases, and magnetic fields are amplified to an approximately dynamically relevant regime. Finally, fragmentation during the collapse is intermittent and mass accretion rates range from 0.2-3 Msun/yr. This suggests that the presence of strongly amplified magnetic fields and turbulence provides additional pressure support on small scales and make the direct collapse a viable scenario for the formation of massive objects under the required ambient conditions.

11 pages, 7 figures, accepted for publication in MNRAS

References in corpus (17)

• A luminous quasar at a redshift of z = 7.085
• Formation of Supermassive Black Holes by Direct Collapse in Pregalactic Halos
• Supermassive black hole formation during the assembly of pre-galactic discs
• A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence
• Fluctuations in the High-Redshift Lyman-Werner Background: Close Halo Pairs as the Origin of Supermassive Black Holes
• Formation of massive black holes in rapidly growing pre-galactic gas clouds
• Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse
• Quasars at z=6: the survival of the fittest
• A three-dimensional deflagration model for Type Ia supernovae confronted with observations
• The Evolution of Supermassive Population III Stars
• Constraining the high redshift formation of black hole seeds in nuclear star clusters with gas inflows
• Formation of massive protostars in atomic cooling haloes
• A UV flux constraint on the formation of direct collapse black holes
• Disk fragmentation and the formation of population III stars
• Comparative statistics of selected subgrid-scale models in large eddy simulations of decaying, supersonic MHD turbulence
• Large-eddy simulations of isolated disc galaxies with thermal and turbulent feedback
• Nonlinear closures for scale separation in supersonic magnetohydrodynamic turbulence