Stellar disc streams as probes of the Galactic potential and satellite
  impacts
  Stars aligned in thin stream-like features (feathers), with widths of
$\delta\sim1-10^{\circ}$ and lengths as large as $\Delta l\sim180^{\circ}$,
have been observed towards the Anticenter of our Galaxy and their properties
mapped in abundances and phase-space. We study their origin by analysing
similar features arising in an N-body simulation of a Galactic disc interacting
with a Sagittarius-like dwarf spheroidal galaxy (Sgr). By following the orbits
of the particles identified as contributing to feathers backwards in time, we
trace their excitation to one of Sgr's previous pericentric passages. These
particles initially span a large range of phase-angles but a tight range of
radii, suggesting they provide a probe of populations in distinct annuli in the
outer Galactic disc. The structures are long lived and persist after multiple
passages on timescales of $\sim4 \,\rm{Gyrs}$. On the sky, they exhibit
oscillatory motion that can be traced with a single orbit mapped over much of
their full length and with amplitudes and gradients similar to those observed.
We demonstrate how these properties of feathers may be exploited to measure the
potential, its flattening, as well as infer the strength of recent potential
perturbations.
