PI: Matthew Middleton

It is becoming well accepted that SMBHs at high redshift must have grown at super- Eddington rates to match observations of black holes with masses of 109 M☉ at z > 6. Exploring this regime of accretion is challenging, as the structure and dynamics of the accretion flow are heavily affected by radiation pressure, whilst the liberated energy from the inflow is highly anisotropic. In this project we deployed the 3D GRMHD code Athena++ to explore the global changes in the flow with super-Eddington accretion rate onto a stellar mass black hole. From our runs we obtained snapshots of the accretion flow (see below) which were then post-processed to obtain a new generation of spectral models. These new models have been successfully applied to data from an ultraluminous X-ray source for the first time (Mills et al. 2024), which is both helping us to understand these systems, and is laying the groundwork for extracting new families of models from forthcoming simulations.

Figure 1: Left hand plot – top view of the super-Eddington accretion flow after ~12,000 light-crossing times in the simulation. Streamlines trace movement in the accretion disc and the colours indicate pseudo-density. Right hand plot – side view (cutting vertically through the accretion disc and only showing one side) of the accretion flow, highlighting the radiatively driven outflow (streamlines, with colours following the horizontal colour bar in units of c).