The effect of Warm Dark Matter on galaxy properties: constraints from
  the stellar mass function and the Tully-Fisher relation
  In this paper we combine high resolution N-body simulations with a semi
analytical model of galaxy formation to study the effects of a possible Warm
Dark Matter (WDM) component on the observable properties of galaxies. We
compare three WDM models with a dark matter mass of 0.5, 0.75 and 2.0 keV, with
the standard Cold Dark Matter case. For a fixed set of parameters describing
the baryonic physics the WDM models predict less galaxies at low (stellar)
masses, as expected due to the suppression of power on small scales, while no
substantial difference is found at the high mass end. However these differences
in the stellar mass function, vanish when different set of parameters are used
to describe the (largely unknown) galaxy formation processes. We show that is
possible to break this degeneracy between DM properties and the
parameterization of baryonic physics by combining observations on the stellar
mass function with the Tully-Fisher relation (the relation between stellar mass
and the rotation velocity at large galactic radii as probed by resolved HI
rotation curves). WDM models with a too warm candidate (m<0.75 keV) cannot
simultaneously reproduce the stellar mass function and the Tully-Fisher
relation. We conclude that accurate measurements of the galaxy stellar mass
function and the link between galaxies and dark matter haloes down to the very
low-mass end can give very tight constraints on the nature of DM candidates.
