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We present a detailed investigation of a number of different approaches to modelling feedback in simulations of galaxy formation. Gas-dynamic forces are evaluated using Smoothed Particle Hydrodynamics (SPH). Star formation and supernova feedback are included using a three parameter model which determines the star formation rate (SFR) normalization, feedback energy and lifetime of feedback regions. The star formation rate is calculated for all gas particles which fall within prescribed temperature, density and convergent flow criteria, and for cosmological simulations we also include a self-gravity criterion for gas particles to prevent star formation at high redshifts. A Lagrangian Schmidt law is used to calculate the star formation rate from the SPH density. Conversion of gas to stars is performed when the star mass for a gas particle exceeds a certain limit, typically half that of the gas particle. Feedback is incorporated by returning a precalculated amount of energy to the ISM as thermal heating. We compare the effects of distributing this energy over the smoothing scale or depositing it on a single particle. Radiative losses are prevented from heated particles by adjusting the density used in radiative cooling so that the decay of energy occurs over a set half-life, or by turning off cooling completely and allowing feedback regions a brief period of adiabatic expansion. We test the models on the formation of galaxies from cosmological
Thacker et al. (Wed,) studied this question.