The orbital structure of a tidally induced bar
  Orbits are the key building blocks of any density distribution and their
study helps us understand the kinematical structure and the evolution of
galaxies. Here we investigate orbits in a tidally induced bar of a dwarf
galaxy, using an $N$-body simulation of an initially disky dwarf galaxy
orbiting a Milky Way-like host. After the first pericenter passage, a tidally
induced bar forms in the stellar component of the dwarf. The bar evolution is
different than in isolated galaxies and our analysis focuses on the period
before it buckles. We study the orbits in terms of their dominant frequencies,
which we calculate in a Cartesian coordinate frame rotating with the bar. Apart
from the well-known x$_1$ orbits we find many other types, mostly with boxy
shapes of various degree of elongation. Some of them are also near-periodic,
admitting frequency ratios of 4/3, 3/2 and 5/3. The box orbits have various
degrees of vertical thickness but only a relatively small fraction of those
have banana (i.e. smile/frown) or infinity-symbol shapes in the edge-on view.
In the very center we also find orbits known from the potential of triaxial
ellipsoids. The elongation of the orbits grows with distance from the center of
the bar in agreement with the variation of the shape of the density
distribution. Our classification of orbits leads to the conclusion that more
than $80 \%$ of them have boxy shapes, while only $8 \%$ have shapes of
classical x$_1$ orbits.
