09/12/2024
Speaker: Yang Luo (Yunnan University, China)
Title: MHD modeling of accretion disks in Direct Collapse scenarios leading to SMBH seeds
Abstract: Direct collapse within dark matter haloes is a promising path for the formation of supermassive black hole (SMBH) seeds at early cosmic times. Utilizing high-resolution zoom-in MHD simulations, we have explored the direct collapse of SMBH seeds within dark matter halos down to a scale of 2 AU. The gas undergoes an isothermal collapse in the outer regions, ultimately forming a central mass core as it becomes optically thick. Our findings demonstrate significant magnetic field amplification during the collapse, and the establishment of the geometrically thick, self-gravitating accretion disk within 0.1 pc, and also the suppression of fragmentation in the disk due to magnetic fields. The accretion disk is affected by magnetorotational instability, further enhancing the magnetic field strength to equipartition levels. We observe that a vertical negative gradient in total vertical stress leads to an equatorial outflow, sandwiched by an inward surface accretion. The development of nonlinear Parker instability, characterized by vertical buckling of field lines, causes material to outflow above the disk. The outflow can clean the gas above the disk and is important for the Lyman-alpha radiation escaping from the dense central area.
Related publication:
Direct Collapse Accretion Disks Within Dark Matter Halos: Saturation of the Magneto-rotational Instability and the Field Expulsion
ui.adsabs.harvard.edu/abs/2024ApJ...976...85L/abstract