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A new mechanism for Galactic disk mixing : Implications to Galactic disk evolution

Ivan Minchev (Obs. de Strasbourg)

We have recently identified a previously unknown radial migration
mechanism resulting from the overlap of spiral and bar resonances in
galactic disks (Minchev & Famaey 2010, Minchev, Famaey et al. 2010).
This new mechanism is much more efficient than mixing by transient
spirals and must exist in all barred galaxies, such as our own Milky
Way. The consequences of this are a strong flattening in the
metallicity gradient in the disk, an extended disk profile, and the
formation of a thick disk component, all taking place in only a couple
of Gyr. This timescale is drastically shorter than previously expected
and thus can put strong constraints on the longevity, strength and
pattern speeds of the Galactic bar and Spiral Structure. Unlike mixing
by transient spirals, migration from resonance overlap
works also in low-mass systems, such as NGC 300 and M33, and can thus
explain the extended disks seen in these galaxies.