Galactic Archaeology with asteroseismic ages: Evidence for delayed gas infall in the formation of the Milky Way disc
Journal
ASTRONOMY & ASTROPHYSICS
Date Issued
2019
Author(s)
Spitoni, E.
•
Silva Aguirre, V.
•
Matteucci, F.
•
CALURA, Francesco
•
GRISONI, Valeria
Abstract
Context. Precise stellar ages from asteroseismology have become available and can help to set stronger constraints on the evolution of the Galactic disc components. Recently, asteroseismology has confirmed a clear age difference in the solar annulus between two distinct sequences in the [α/Fe] versus [Fe/H] abundance ratios relation: the high-α and low-α stellar populations.
Aims: We aim to reproduce these new data with chemical evolution models including different assumptions for the history and number of accretion events.
Methods: We tested two different approaches: a revised version of the "two-infall" model where the high-α phase forms by a fast gas accretion episode and the low-α sequence follows later from a slower gas infall rate, and the parallel formation scenario where the two disc sequences form coevally and independently.
Results: The revised two-infall model including uncertainties in age and metallicity is capable of reproducing: i) the [α/Fe] versus [Fe/H] abundance relation at different Galactic epochs, ii) the age-metallicity relation and the time evolution [α/Fe]; iii) the age distribution of the high-α and low-α stellar populations, iv) the metallicity distribution function. The parallel approach is not capable of properly reproducing the stellar age distribution, in particular at old ages.
Conclusions: The best chemical evolution model is the revised two-infall one, where a consistent delay of ∼4.3 Gyr in the beginning of the second gas accretion episode is a crucial assumption to reproduce stellar abundances and ages.
Aims: We aim to reproduce these new data with chemical evolution models including different assumptions for the history and number of accretion events.
Methods: We tested two different approaches: a revised version of the "two-infall" model where the high-α phase forms by a fast gas accretion episode and the low-α sequence follows later from a slower gas infall rate, and the parallel formation scenario where the two disc sequences form coevally and independently.
Results: The revised two-infall model including uncertainties in age and metallicity is capable of reproducing: i) the [α/Fe] versus [Fe/H] abundance relation at different Galactic epochs, ii) the age-metallicity relation and the time evolution [α/Fe]; iii) the age distribution of the high-α and low-α stellar populations, iv) the metallicity distribution function. The parallel approach is not capable of properly reproducing the stellar age distribution, in particular at old ages.
Conclusions: The best chemical evolution model is the revised two-infall one, where a consistent delay of ∼4.3 Gyr in the beginning of the second gas accretion episode is a crucial assumption to reproduce stellar abundances and ages.
Volume
623
Start page
A60
Issn Identifier
0004-6361
Ads BibCode
2019A&A...623A..60S
Rights
open.access