The cold dark matter content of Galactic dwarf spheroidals: no cores, no
  failures, no problem
  We examine the dark matter content of satellite galaxies in Lambda-CDM
cosmological hydrodynamical simulations of the Local Group from the APOSTLE
project. We find excellent agreement between simulation results and estimates
for the 9 brightest Galactic dwarf spheroidals (dSphs) derived from their
stellar velocity dispersions and half-light radii. Tidal stripping plays an
important role by gradually removing dark matter from the outside in, affecting
in particular fainter satellites and systems of larger-than-average size for
their luminosity. Our models suggest that tides have significantly reduced the
dark matter content of Can Ven I, Sextans, Carina, and Fornax, a prediction
that may be tested by comparing them with field galaxies of matching luminosity
and size. Uncertainties in observational estimates of the dark matter content
of individual dwarfs have been underestimated in the past, at times
substantially. We use our improved estimates to revisit the `too-big-to-fail'
problem highlighted in earlier N-body work. We reinforce and extend our
previous conclusion that the APOSTLE simulations show no sign of this problem.
The resolution does not require `cores' in the dark mass profiles, but, rather,
relies on revising assumptions and uncertainties in the interpretation of
observational data and accounting for `baryon effects' in the theoretical
modelling.
