Ionisation Feedback in Star and Cluster Formation Simulations
  Feedback from photoionisation may dominate on parsec scales in massive
star-forming regions. Such feedback may inhibit or enhance the star formation
efficiency and sustain or even drive turbulence in the parent molecular cloud.
Photoionisation feedback may also provide a mechanism for the rapid expulsion
of gas from young clusters' potentials, often invoked as the main cause of
'infant mortality'. There is currently no agreement, however, with regards to
the efficiency of this process and how environment may affect the direction
(positive or negative) in which it proceeds. The study of the photoionisation
process as part of hydrodynamical simulations is key to understanding these
issues, however, due to the computational demand of the problem, crude
approximations for the radiation transfer are often employed. We will briefly
review some of the most commonly used approximations and discuss their major
drawbacks. We will then present the results of detailed tests carried out using
the detailed photoionisation code MOCASSIN and the SPH+ionisation code iVINE
code, aimed at understanding the error introduced by the simplified
photoionisation algorithms. This is particularly relevant as a number of new
codes have recently been developed along those lines. We will finally propose a
new approach that should allow to efficiently and self-consistently treat the
photoionisation problem for complex radiation and density fields.
