Evolutionary tracks of tidally stirred disky dwarf galaxies
  Using collisionless N-body simulations, we investigate the tidal evolution of
late-type, rotationally supported dwarfs inside Milky Way-sized host galaxies.
Our study focuses on a wide variety of dwarf orbital configurations and initial
structures. During the evolution, the disky dwarfs undergo strong mass loss,
the stellar disks are transformed into spheroids, and rotation is replaced by
random motions of the stars. Thus, the late-type progenitors are transformed
into early-type dwarfs as envisioned by the tidal stirring model for the
formation of dwarf spheroidal (dSph) galaxies in the Local Group. We determine
the photometric properties of the dwarfs, including the total visual magnitude,
the half-light radius and the central surface brightness as they would be
measured by an observer near the galactic center. Special emphasis is also
placed on studying their kinematics and shapes. We demonstrate that the
measured values are biased by a number of observational effects including the
increasing angle of the observation cone near the orbital pericenter, the fact
that away from the pericenter the tidal tails are typically oriented along the
line of sight, and the fact that for most of the evolution the stellar
components of the dwarfs are triaxial ellipsoids whose major axis tumbles with
respect to the line of sight. Finally, we compare the measured properties of
the simulated dwarfs to those of dwarf galaxies in the Local Group. The
evolutionary tracks of the dwarfs in different parameter planes and the
correlations between their different properties, especially the total magnitude
and the surface brightness, strongly suggest that present-day dSph galaxies may
have indeed formed from late-type progenitors as proposed by the tidal stirring
scenario.
