A simple way to improve AGN feedback prescription in SPH simulations
  AGN feedback is an important ingredient in galaxy evolution, however its
treatment in numerical simulations is necessarily approximate, requiring
subgrid prescriptions due to the dynamical range involved in the calculations.
We present a suite of SPH simulations designed to showcase the importance of
the choice of a particular subgrid prescription for AGN feedback. We
concentrate on two approaches to treating wide-angle AGN outflows: thermal
feedback, where thermal and kinetic energy is injected into the gas surrounding
the SMBH particle, and virtual particle feedback, where energy is carried by
tracer particles radially away from the AGN. We show that the latter model
produces a far more complex structure around the SMBH, which we argue is a more
physically correct outcome. We suggest a simple improvement to the thermal
feedback model - injecting the energy into a cone, rather than spherically
symmetrically - and show that this markedly improves the agreement between the
two prescriptions, without requiring any noticeable increase in the
computational cost of the simulation.
