A and F stars can be used as probes of outer Galactic disk kinematics : here we extend the work of by crossmatching their A/F sample with Gaia DR2 to bring in proper motions .
These are combined with the already measured radial velocities and spectro-photometric distances to obtain full space motions .
We use this sample of 1173 stars , located in two pencil-beam sightlines ( \ell = 178 ^ { \circ } and \ell = 118 ^ { \circ } ) , to sample the Galactocentric velocity field out to almost R _ { G } = 15 kpc .
We find there are significant differences in all three ( radial , azimuthal and vertical ) kinematic components between the two directions .
The rotation curve is roughly flat in the anticentre direction , confirming and extending the result of thanks to the greater reach of our spectro-photometric distance scale .
However at \ell = 118 ^ { \circ } the circular velocity rises outwards from R _ { G } = 10.5 kpc and there is a more pronounced gradient in radial motion than is seen at \ell = 178 ^ { \circ } .
Furthermore , the A star radial motion differs from the F stars by \sim 10 km s ^ { -1 } .
We discuss our findings in the context of perturbers potentially responsible for the trends , such as the central bar , spiral arms , the warp and external satellites .
Our results at \ell = 178 ^ { \circ } are broadly consistent with previous work on K giants in the anticentre , but the kinematics at \ell = 118 ^ { \circ } in the Perseus region do not yet reconcile easily with bar or spiral arm perturbation .