Abstract
We study the role of radial motions of stars and gas on the evolution of abundance profiles in the Milky Way disk. We investigate, in a parametrized way, the impact of radial flows of gas and radial migration of stars induced mainly by the Galactic bar and its iteraction with the spiral arms. We use a model with several new or up-dated ingredients (atomic and molecular gas phases, star formation depending on molecular gas, recent sets of metallicity-dependent stellar yields from H to Ni, observationally inferred SNIa rates), which reproduces well most global and local observables of the Milky Way. We obtain abundance profiles flattening both in the inner disk (because of radial flows) and in the outer disk (because of the adopted star formation law). The gas abundance profiles flatten with time, but the corresponding stellar profiles appear to be steeper for younger stars, because of radial migration. We find a correlation between the stellar abundance profiles and O/Fe, which is a proxy for stellar age. Our final abundance profiles are in overall agreement with observations, but slightly steeper (by 0.01-0.02 dex/kpc) for elements above S. We find an interesting "odd-even effect" in the behaviour of the abundance profiles (steeper slopes for odd elements) for all sets of stellar yields; however, this behaviour does not appear in observations, suggesting that the effect is, perhaps, overestimated in current stellar nucleosynthesis calculations.
Highlights
The abundance profiles of chemical elements constitute one of the key properties of galactic disks
Most semi-analytical studies of abundance profiles were performed in the framework of the so-called “independent-ring” model, where the galactic disk is simulated as an ensemble of independently evolving annuli (e.g. Guesten & Mezger 1982; Tosi 1988; Matteucci et al 1989; Ferrini et al 1994; Prantzos & Aubert 1995; Prantzos et al 1996; Chiappini et al 1997; Boissier & Prantzos 1999; Hou et al 2000; Prantzos & Boissier 2000) and concerned the Milky Way (MW) disk, for which a large number of other constraints, both local and global ones are available
In KPA15 we have found that the adopted parameters of the model (SFR efficiency, infall timescale, SNIa rate, initial mass function (IMF), etc.) allow us to reproduce the solar abundance of O and Fe for the average 4.5 Gyr old star in the solar neighbourhood3 The average birth radius of those stars is found to be at a Galactocentric distance of ∼6.5 kpc, i.e. ∼1.5 kpc inwards from the present day position of the Sun
Summary
The abundance profiles of chemical elements constitute one of the key properties of galactic disks. Guesten & Mezger 1982; Tosi 1988; Matteucci et al 1989; Ferrini et al 1994; Prantzos & Aubert 1995; Prantzos et al 1996; Chiappini et al 1997; Boissier & Prantzos 1999; Hou et al 2000; Prantzos & Boissier 2000) and concerned the Milky Way (MW) disk, for which a large number of other constraints, both local and global ones are available Those studies focused mainly on the interplay between the local star formation and infall rates, or on the impact of variable stellar initial mass function (IMF). All models explicitly consider Fe production by SNIa (albeit with different prescriptions for the SNIa rate) and the finite lifetimes of stars Despite those differences, all three models find good agreement with the main observables of the MW, both locally (dispersion in age-metallicity relation, metallicity distribution, the characteristic “two-branch” behaviour between thick and thin disk in the O/Fe vs Fe/H plane) and globally (stellar and abundance profiles).
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