High Galactic latitude runaway stars as tracers of the spiral arms

A direct observation of the spiral structure of the Galaxy is hindered by our position in the middle of the Galactic plane. We propose a method based on the analysis of the birthplaces of high Galactic latitude runaway stars to map the spiral arms and determine their dynamics. As a proof of concept, the method is applied to a local sample of early-type stars and a sample of runaways stars to obtain estimates of the pattern speed (Ωp,local = 20.3± 0.5 kms −1 kpc and Ωp,runaway = 21.9 ± 8.6 km s −1 kpc) and the spiral arm’s phase angle (φlocal = −53.1 ◦ ±3.1◦ and φrunaway = −63.5 ◦ ±22.5◦). We also estimate the performance of this method once the data gathered by Gaia, in particular for runaway stars observed on the other side of the Galaxy, is available.