The Origin of the Hubble Sequence in Lambda-CDM Cosmology
  The Galform semi-analytic model of galaxy formation is used to explore the
mechanisms primarily responsible for the three types of galaxies seen in the
local universe: bulge, bulge+disk and disk, identified with the visual
morphological types E, S0/a-Sbc, and Sc-Scd, respectively. With a suitable
choice of parameters the Galform model can accurately reproduce the observed
local K_s-band luminosity function (LF) for galaxies split by visual
morphological type. The successful set of model parameters is used to populate
the Millennium Simulation with 9.4 million galaxies and their dark matter
halos. The resulting catalogue is then used to explore the evolution of
galaxies through cosmic history. The model predictions concur with recent
observational results including the galaxy merger rate, the star formation rate
and the seemingly anti-hierarchical evolution of ellipticals. However, the
model also predicts significant evolution of the elliptical galaxy LF that is
not observed. The discrepancy raises the possibility that samples of z~1
galaxies which have been selected using colour and morphological criteria may
be contaminated with galaxies that are not actually ellipticals.
