Evolution of dwarf spheroidal satellites in the common surface-density
  dark halos
  We investigate the growth histories of dark matter halos associated with
dwarf satellites in Local Group galaxies and the resultant evolution of the
baryonic component. Our model is based on the recently proposed property that
the mean surface density of a dark halo inside a radius at maximum circular
velocity V_max is universal over a large range of V_max. Following that this
surface density of 20 Msun/pc^2 well explains dwarf satellites in the Milky Way
and Andromeda, we find that the evolution of the dark halo in this common
surface-density scale is characterized by the rapid increase of the halo mass
assembled by the redshift z_TT of the tidal truncation by its host halo, at
early epochs of z_TT >~ 6 or V_max <~ 22 km/s. This mass growth of the halo is
slow at lower z_TT or larger V_max. Taking into account the baryon content in
this dark halo evolution, under the influence of the ionizing background
radiation, we find that the dwarf satellites are divided into roughly two
families: those with V_max <~ 22 km/s having high star formation efficiency and
those with larger V_max having less efficient star formation. This
semi-analytical model is in good agreement with the high-resolution numerical
simulation for galaxy formation and with the observed star formation histories
for Fornax and Leo~II. This suggests that the evolution of a dark halo plays a
key role in understanding star formation histories in dwarf satellites.
