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(Abridged) We use N-body simulations to study the evolution of dwarfspheroidal galaxies (dSphs) driven by galactic tides. We adopt acosmologically-motivated model where dSphs are approximated by a King modelembedded within an NFW halo. We find that these NFW-embedded King models areextraordinarily resilient to tides; the stellar density profile still resemblesa King model even after losing more than 99% of the stars. As tides strip thegalaxy, the stellar luminosity, velocity dispersion, central surfacebrightness, and core radius decrease monotonically. Remarkably, we find thatthe evolution of these parameters is solely controlled by the total amount ofmass lost from within the luminous radius. Of all parameters, the core radiusis the least affected: after losing 99% of the stars, R_c decreases by just afactor of ~2. Interestingly, tides tend to make dSphs more dark-matterdominated because the tightly bound central dark matter ``cusp'' is moreresilient to disruption than the ``cored'' King profile. We examine whether theextremely large M/L ratios of the newly-discovered ultra-faint dSphs might havebeen caused by tidal stripping of once brighter systems. Although dSph tidalevolutionary tracks parallel the observed scaling relations in theluminosity-radius plane, they predict too steep a change in velocity dispersioncompared with the observational estimates hitherto reported in the literature.The ultra-faint dwarfs are thus unlikely to be the tidal remnants of systemslike Fornax, Draco, or Sagittarius. Despite spanning four decades inluminosity, dSphs appear to inhabit halos of comparable peak circular velocity,lending support to scenarios that envision dwarf spheroidals as able to formonly in halos above a certain mass threshold.

The Tidal Evolution of Local Group Dwarf Spheroidals