Spiral arm lanes as seen from young and old stellar tracers

Abstract

In this work we compare the spiral structure depicted by two stellar tracers with very different ages: an extremely young population of OB type stars and a population of Red Clump stars assumed to be relaxed in the Galactic potential. A Kernel density estimator applied to Gaia and StarHorse EDR3 data allow us to trace the over/under-density maps on the Galactic plane at± 3 kpc from the Sun location. Preliminary results confirm that Perseus and Sagittarius-Carina arms are well delineated in both samples and possible offsets between their locus are evaluated. More important, the surface density amplitude of the young population is estimated to be a factor 2-3 larger than that of the old population. These results provide new insights to discern on the mechanisms by which the Milky Way spiral arms evolve