Cosmological galaxy formation simulations using smoothed particle hydrodynamics

Abstract

We present the McMaster Unbiased Galaxy Simulations (MUGS), the first nine galaxies of an unbiased selection ranging in total mass from 5 × 10 11 M ⊙ to 2 × 10 12 M ⊙ simulated using N -body smoothed particle hydrodynamics at high resolution. The simulations include a treatment of low-temperature metal cooling, UV background radiation, star formation and physically motivated stellar feedback. Mock images of the simulations show that the simulations lie within the observed range of relations such as that between colour and magnitude and that between brightness and circular velocity (Tully–Fisher). The greatest discrepancy between the simulated galaxies and observed galaxies is the high concentration of material at the centre of the galaxies as represented by the centrally peaked rotation curves and the high bulge-to-total ratios of the simulations determined both kinematically and photometrically. This central concentration represents the excess of low angular momentum material that long has plagued morphological studies of simulated galaxies and suggests that higher resolutions and a more accurate description of feedback will be required to simulate more realistic galaxies. Even with the excess central mass concentrations, the simulations suggest the important role merger history and halo spin play in the formation of discs.