A WEAVE Radial Velocity Survey to Unravel the Nature of the Milky Way's Spiral Arms

The nature of the spiral arms of our Milky Way Galaxy is still a matter of debate. Different theories have been suggested (density waves, swing amplification, invariant manifolds...) which impose several constraints on the observables. For the first time it will be possible to disentangle these theories by combining Gaia and WEAVE data. Great advantage comes from the fact that WEAVE is in the Northern Hemisphere, that is with good coverage towards the galactic anticenter. We plan to quantify the kinematic perturbation induced by the Perseus spiral arm through radial velocity measurements. We show how, for the first time, we have detected the stellar overdensity associated with the Perseus arm using a Stromgren photometric survey with the Wide Field Camera on the Isaac Newton Telescope. This survey has allowed us to perform first tests on WEAVE capabilities.