Simulating the formation of the local galaxy population

We simulate the formation and evolution of the local galaxy population, starting from initial conditions with a smoothed linear density field which matches that derived from the IRAS 1.2-Jy galaxy survey. Our simulations track the formation and evolution of all dark matter haloes more massive than 1011 M⊙ out to a distance of 8000 km s−1 from the Milky Way. We implement prescriptions similar to those of Kauffmann et al. to follow the assembly and evolution of the galaxies within these haloes. We focus on two variants of the CDM cosmology: a ΛCDM model and a τCDM model. Galaxy formation in each is adjusted to reproduce the I-band Tully–Fisher relation of Giovanelli et al. We compare the present-day luminosity functions, colours, morphology and spatial distribution of our simulated galaxies with those of the real local population, in particular with the Updated Zwicky Catalog, with the IRAS PSCz redshift survey, and with individual local clusters such as Coma, Virgo and Perseus. We also use the simulations to study the clustering bias between the dark matter and galaxies of differing type. Although some significant discrepancies remain, our simulations recover the observed intrinsic properties and the observed spatial distribution of local galaxies reasonably well. They can thus be used to calibrate methods which use the observed local galaxy population to estimate the cosmic density parameter or to draw conclusions about the mechanisms of galaxy formation. To facilitate such work, we publicly release our z=0 galaxy catalogues, together with the underlying mass distribution.