Testing core creation in hydrodynamical simulations using the HI
  kinematics of field dwarfs
  The majority of recent hydrodynamical simulations indicate the creation of
central cores in the mass profiles of low-mass halos, a process that is
attributed to star formation-related baryonic feedback. Core creation is
regarded as one of the most promising solutions to potential issues faced by
the lambda cold dark matter (LambdaCDM) cosmology on small scales. For example,
the reduced dynamical mass enclosed by cores can explain the low rotational
velocities measured for nearby dwarf galaxies, thus possibly lifting the
seeming contradiction with the LambdaCDM expectations (the so-called "too big
to fail" problem). Here we test core creation as a solution of cosmological
issues by using a sample of dwarfs with measurements of their atomic hydrogen
(HI) kinematics extending to large radii. Using the NIHAO hydrodynamical
simulation as an example, we show that core creation can successfully reproduce
the kinematics of dwarfs with small kinematic radii, R <~ 1.5 kpc. However, the
agreement with observations becomes poor once galaxies with kinematic
measurements extending beyond the core region, R ~ 1.5 - 4 kpc, are considered.
This result illustrates the importance of testing the predictions of
hydrodynamical simulations that are relevant for cosmology against a broad
range of observational samples. We would like to stress that our result is
valid only under the following set of assumptions: i) that our sample of dwarfs
with HI kinematics is representative of the overall population of field dwarfs,
ii) that there are no severe measurement biases in the observational parameters
of our HI dwarfs (e.g., related to inclination estimates), and iii) that the HI
velocity fields of dwarfs are regular enough to allow the recovery of the true
enclosed dynamical mass.
