The effect of radial migration on galactic disks

CARLOS VERA-CIRO, ELENA D'ONGHIA, JULIO F. NAVARRO, MARIO G. ABADI

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Chicago; Año: 2014 vol. 794 p. 173 - 181

0004-637X

We study the radial migration of stars driven by recurring multi-arm spiral features in an exponential disk embeddedin a dark matter halo. The spiral perturbations redistribute angular momentum within the disk and lead to substantialradial displacements of individual stars, in a manner that largely preserves the circularity of their orbits and thatresults, after 5 Gyr (∼40 full rotations at the disk scale length), in little radial heating and no appreciable changes tothe vertical or radial structure of the disk. Our results clarify a number of issues related to the spatial distribution andkinematics of migrators. In particular, we find that migrators are a heavily biased subset of stars with preferentiallylow vertical velocity dispersions. This ?provenance bias? for migrators is not surprising in hindsight, for stars withsmall vertical excursions spend more time near the disk plane, and thus respond more readily to non-axisymmetricperturbations. We also find that the vertical velocity dispersion of outward migrators always decreases, whereasthe opposite holds for inward migrators. To first order, newly arrived migrators simply replace stars that havemigrated off to other radii, thus inheriting the vertical bias of the latter. Extreme migrators might therefore berecognized, if present, by the unexpectedly small amplitude of their vertical excursions. Our results show thatmigration, understood as changes in angular momentum that preserve circularity, can strongly affect the thin disk,but cast doubts on models that envision the Galactic thick disk as a relic of radial migration.