  GalICS 2.0 is a new semianalytic code to model the formation and evolution of
galaxies in a cosmological context. N-body simulations based on a Planck
cosmology are used to construct halo merger trees, track subhaloes, compute
spins and measure concentrations. The accretion of gas onto galaxies and the
morphological evolution of galaxies are modelled with prescriptions derived
from hydrodynamic simulations. Star formation and stellar feedback are
described with phenomenological models (as in other semianalytic codes). GalICS
2.0 computes rotation speeds from the gravitational potential of the dark
matter, the disc and the central bulge. As the rotation speed depends not only
on the virial velocity but also on the ratio of baryons to dark matter within a
galaxy, our calculation predicts a different Tully-Fisher relation from models
in which the rotation speed is proportional to the virial velocity. This is why
GalICS 2.0 is able to reproduce the galaxy stellar mass function and the
Tully-Fisher relation simultaneously. Our results are also in agreement with
halo masses from weak lensing and satellite kinematics, gas fractions, the
relation between star formation rate (SFR) and stellar mass, the evolution of
the cosmic SFR density, bulge-to-disc ratios, disc sizes and the Faber-Jackson
relation.
