In this letter we examine the evolution of the radial metallicity gradientinduced by secular processes, in the disk of an $N$-body Milky Way-like galaxy.We assign a [Fe/H] value to each particle of the simulation according to aninitial, cosmologically motivated, radial chemical distribution and let thedisk dynamically evolve for 6 Gyr. This direct approach allows us to take intoaccount only the effects of dynamical evolution and to gauge how and to whatextent they affect the initial chemical conditions. The initial [Fe/H]distribution increases with R in the inner disk up to R ~ 10 kpc and decreasesfor larger R. We find that the initial chemical profile does not undergo majortransformations after 6 Gyr of dynamical evolution. The final radial chemicalgradients predicted by the model in the solar neighborhood are positive and ofthe same order of those recently observed in the Milky Way thick disk. We conclude that: 1) the spatial chemical imprint at the time of diskformation is not washed out by secular dynamical processes, and 2) the observedradial gradient may be the dynamical relic of a thick disk originated from astellar population showing a positive chemical radial gradient in the innerregions.
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