The impact of baryons on dark matter haloes
  We analyse the dark matter (DM) distribution in a approx 10^12 M_sun halo
extracted from a simulation consistent with the concordance cosmology, where
the physics regulating the transformation of gas into stars was allowed to
change producing galaxies with different morphologies. Although the DM profiles
get more concentrated as baryons are collected at the centre of the haloes
compared to a pure dynamical run, the total baryonic mass alone is not enough
to fully predict the reaction of the DM profile. We also note that baryons
affect the DM distribution even outside the central regions. Those systems
where the transformation of gas into stars is regulated by Supernova (SN)
feedback, so that significant disc structures are able to form, are found to
have more concentrated dark matter profiles than a galaxy which has efficiently
transformed most of its baryons into stars at early times. The accretion of
satellites is found to be associated with an expansion of the dark matter
profiles, triggered by angular momentum transfer from the incoming satellites.
As the impact of SN feedback increases, the satellites get less massive and are
even strongly disrupted before getting close to the main structure causing less
angular momentum transfer. Our findings suggest that the response of the DM
halo is driven by the history of assembly of baryons into a galaxy along their
merger tree.
