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Accepted for publication in MNRAS Galaxy mergers have been investigated for decades using smoothed particle hydrodynam-ics (SPH), but recent work highlighting inaccuracies inherent in the traditional SPH technique calls into question the reliability of previous studies. We explore this issue by comparing a suite of GADGET-3 SPH simulations of idealised (i.e., non-cosmological) isolated discs and galaxy mergers with otherwise identical calculations performed using the moving-mesh code AREPO. When black hole (BH) accretion and active galactic nucleus (AGN) feedback are not included, the star formation histories (SFHs) obtained from the two codes agree well. When BHs are included, the code- and resolution-dependent variations in the SFHs are more sig-nificant, but the agreement is still good, and the stellar mass formed over the course of a simulation is robust to variations in the numerical method. During a merger, the gas morphol-ogy and phase structure are initially similar prior to the starburst phase. However, once a hot gaseous halo has formed from shock heating and AGN feedback (when included), the agree-ment is less good. In particular, during the post-starburst phase, the SPH simulations feature
Hayward et al. (Tue,) studied this question.