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We examine the dark matter content of satellite galaxies in Lambda-CDMcosmological hydrodynamical simulations of the Local Group from the APOSTLEproject. We find excellent agreement between simulation results and estimatesfor the 9 brightest Galactic dwarf spheroidals (dSphs) derived from theirstellar velocity dispersions and half-light radii. Tidal stripping plays animportant role by gradually removing dark matter from the outside in, affectingin particular fainter satellites and systems of larger-than-average size fortheir luminosity. Our models suggest that tides have significantly reduced thedark matter content of Can Ven I, Sextans, Carina, and Fornax, a predictionthat may be tested by comparing them with field galaxies of matching luminosityand size. Uncertainties in observational estimates of the dark matter contentof individual dwarfs have been underestimated in the past, at timessubstantially. We use our improved estimates to revisit the `too-big-to-fail'problem highlighted in earlier N-body work. We reinforce and extend ourprevious 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 ofobservational data and accounting for `baryon effects' in the theoreticalmodelling.

The cold dark matter content of Galactic dwarf spheroidals: no cores, no failures, no problem