The method by which this simulation is realized involves calculating the radiation field in five bands; magnetic field; gravitational field; turbulence; chemical abundances; dust destruction and heating/cooling balance in each gas cell. FIRE was designed to simulate galaxies, while STARFORGE was created to study clouds within the interstellar medium. However, in terms of physics, the codes diverge only in how they treat ‘stars’ in the simulation, with STARFORGE incorporating single star particles (appropriate for low cell masses or high resolution) and FIRE considering stellar population particles (appropriate for cell masses >1 M⊙ or lower resolutions). Each code calculates the mass, momentum, energy, cosmic ray and photon fluxes for each type of star particle and updates the simulation grid accordingly.
With such a comprehensive simulation of a black hole’s environment, it becomes possible to understand which physical processes are important on different scales. For instance, to determine the dynamics of the system, gravity plays a key role. On scales larger than the accretion disk, self-gravity governs the inflow rates towards the black hole. On smaller scales, accurate gravitational orbit integration is crucial. Magnetic fields play a minor role in overall gas dynamics, not only on ≳100 pc scales, as previously known, but down to ~1 pc scales. However, magnetic fields are critical for the structure and size of the accretion disk. Star formation is important on 0.1–104 pc scales, but can be treated well by a ‘galactic star formation’ model for most of the range; it is only the 0.1–1 pc region where resolved star formation physics becomes necessary. On smaller scales still, star formation is strongly suppressed.
This is a preview of subscription content, access via your institution