Visitor: dr. Emanuele Spitoni
Dates: June 27-July 10, 2019
In a recent paper, Spitoni et al. (2019, A&A, 623, 60) used a chemical evolution model of the Milky Way Galaxy to study the two distinct sequences in the [alpha/Fe] versus [Fe/H] plane observed by APOGEE in thin and thick disc stars. The recent APOGEE data come also with accurate age determinations as provided by asteroseismology (Silva Aguirre et al. 2018). The interpretation of the asteroseismology+APOGEE data of Spitoni et al. (2019) outlined a new astro-archeological scenario for the formation of the MW discs, in particular constrained neatly the delay between the first and second infall events, which gave place to the high-alpha/Fe and low-alpha/Fe sequence, respectively, in the [alpha/Fe]-[Fe/H] plane. By means of a cosmological semi-analytic model (SAM), Calura & Menci (2009, MNRAS, 400, 1347) qualitatively accounted for the presence of more than one sequence in the [alpha/Fe]-[Fe/H] plane of the MW. The aim of the visit is to deepen the original study of Calura & Menci (2009) of chemical evolution in a cosmological framework, to strengthen the constraints on the MW accretion history in the light of the wealth of new data collected in the last few years. The implementation of a chemical evolution model in a SAM will be fundamental also to study the abundance pattern of the accreted satellites newly discovered thanks to the second Gaia Data Release, i. e. Enceladus (Vincenzo, Spitoni, Calura et al. 2019, MNRAS, in press, arXiv:1903.03465) and Sequoia (Myeong et al. 2019, arXiv:1904.03185). It has been argued from dynamical arguments that such accretion events were accompanied to the appearance of several GCs in the Milky Way halo; for this reason, our planned study of such systems is highly valuable also in the context of studies of globular clusters (GCs), carried on at the OAS by various groups.