Trapped orbits and solar-neighbourhood kinematics
  Torus mapping yields constants of motion for stars trapped at a resonance.
Each such constant of motion yields a system of contours in velocity space at
the Sun and neighbouring points. If Jeans' theorem applied to resonantly
trapped orbits, the density of stars in velocity space would be equal at all
intersections of any two contours. A quantitative measure of the violation of
this principal is defined and used to assess various pattern speeds for a model
of the bar recently fitted to observations of interstellar gas. Trapping at
corotation of a bar with pattern speed in the range 33-36 /Gyr is favoured and
trapping at the outer Lindblad resonance is disfavoured. As one moves around
the Sun the structure of velocity space varies quite rapidly, both as regards
the observed star density and the zones of trapped orbits. The data seem
consistent with trapping at corotation.
