AGN jets and black hole spin in hydrodynamical simulations

Model summary

The main feature of this model, in terms of the effects on galaxy populations, is the addition of an AGN jet mode of feedback. In order to launch realistic jets, black hole spin is tracked and evolved for all BH particles in the simulation.

Jet powers, in addition to depending on spin, also depend on which accretion state the black hole is in. We include three accretion states: the thick, thin and slim disk. The thick disk appears at low accretion rates, has very strong jets and is inefficient at spinning up the black hole. The thin disk, appearing at intermediate accretion rates, has weak jets, strong radiation and efficiently spins up the black hole. The slim disk, corresponding to super-Eddington accretion, has features of both, and has both strong radiation and jets. Slim disks can be turned off in the model, but the thick and thin disks are intimitely tied to their feedback modes (jets and radiation, respectively).

In theory.rst we outline all of the theory which is implemented as part of the model. This includes when the black holes transition from one state to another, the strength of feedback in each state, how spin is evolved in terms of magnitude and direction, etc. In numerics.rst we discuss how jet launching is implemented, and additional black hole time steps introduced into the code. In params.rst we list and discuss all parameters used by the model. In output.rst we list additional arrays output for the BHs and tracers. Below we outline how to configure and run the model.

Compiling and running the model

The model can be run with either the EAGLE or COLIBRE models. You can configure the model with --with-black-holes=SPIN_JET in combination with other configure options, or you can configure the full EAGLE or COLIBRE models with the new spin/jet physics as --with-subgrid=SPIN_JET_EAGLE and --with-subgrid=SPIN_JET_COLIBRE, respectively. The model will then run as long as --black-holes is among the runtime options.

For cosmological simulations you do not need to do anything special, but for isolated runs (or any runs with black holes in the initial conditions), the ICs must include two new fields for all black holes: a scalar field representing black hole spins called Spins and a vector field representing the directions of the spin called AngularMomentumDirections. The former should be between 0 and 1, while the latter should be normalized to 1.

A full list of all relevant parameters of the model is in params.rst. We also briefly describe the most important parameters which need to be set to run the model, as well as how to run it in different configurations.