Emanuele Spitoni (Nice Observatory): The [α/Fe] bimodality in the Milky Way disc with chemical evolution models

Thursday 7 Apr 2022, 14:00 → 15:00 Europe/Stockholm

https://uu-se.zoom.us/j/62091586806

Title: The [α/Fe] bimodality in the Milky Way disc with chemical evolution models
Speaker: Emanuele Spitoni
Affiliation: Nice Observatory
Time: Thursday 7 April 2022, 1400 to 1500
Location: online at https://uu-se.zoom.us/j/62091586806

Abstract:

The analysis of the data of diverse spectroscopic surveys such as  Gaia-ESO, APOGEE, GALAH    suggests the existence of a clear distinction between two sequences of disc stars at different Galactocentric distances in the [α/Fe] vs. [Fe/H] abundance ratio space: the so-called high-α sequence, classically associated to an old population of stars in the thick disc, and the low-α sequence, which mostly comprises relatively young stars in the thin disc. We present a  multi-zone chemical evolution model designed for regions at different Galactocentric distances using measured chemical abundances from the APOGEE DR16 sample. In the outer disc (with radii R>6 kpc), the chemical dilution due to a late accretion event of gas with primordial chemical composition is the main driver of the [Mg/Fe] vs. [Fe/H] abundance pattern in the low-α sequence. In the inner disc, in the framework of the two-infall model, we confirm the presence of an enriched gas infall in the low-α phase as suggested by chemo-dynamical models. Our analysis based on the recent APOGEE DR16 data suggests a significant delay time, ranging from ∼3.0 to 4.7 Gyr, between the first and second gas infall events for all the analyzed Galactocentric regions, confirming the findings of previous works for the solar neighbourhood based on the APOKASC data.  Recent results on the connection between the disc dichotomy signature in the vertical distribution of  [Mg/Fe] abundance ratio and the delayed infall scenario in the solar neighbourhood will be also discussed.