Baryons Shaping Dark Matter Haloes
  In this work we aim at investigating the effects of baryons on the dark
matter (DM) haloes structure, focusing on the correlation between the presence
and importance of stellar discs and the halo shapes. We study the properties of
a subsample of DM haloes from Fenix and EAGLE cosmological simulations. We
inspect the central regions of haloes in the mass range [10.9 - 992.3] x
10^{10} Msun at z=0, comparing the hydrodynamic runs and their dark matter only
(DMo) counterparts. Our results indicate that baryons have a significant impact
on the shape of the inner halo, mainly within ~ 20 percent of the virial
radius. We find haloes to be more spherical when hosting baryons. While the
impact of baryons depends on the mass of the haloes, we also find a trend with
morphology which suggests that the way baryons are assembled is also relevant
in agreement with previous works. Our findings also indicate that disc galaxies
preferentially form in haloes whose DMo counterparts were originally more
spherical and with stronger velocity anisotropy. The presence of baryons alter
the orbital structure of the DM particles of the haloes, which show a decrease
in their velocity anisotropy, towards more tangentially biased orbits. This
relative decrease is weaker in the case of disc-dominated galaxies. Our results
point out to a cosmological connection between the final morphology of galaxies
and the intrinsic properties of their DM haloes, which gets reinforce by the
growth of the discs.
