The dual origin of the Galactic thick disc and halo from the gas-rich Gaia–Enceladus Sausage merger

• DOI: 10.1093/mnras/staa2057
• Publication Date: 2020-07-10T19:11:02Z
• Authors: Robert J J Grand; Daisuke Kawata; Vasily Belokurov; Alis J Deason; Azadeh Fattahi; Francesca Fragkoudi; Facundo A Gómez; Federico Marinacci; Rüdiger Pakmor
• Keywords: Satellite galaxy

We analyse a set of cosmological magneto-hydrodynamic simulations the formation Milky Way-mass galaxies identified to have prominent radially anisotropic stellar halo component similar so-called "Gaia Sausage" found in Gaia data. examine effects progenitor Sausage (the Gaia-Enceladus-Sausage, GES) on major galactic components analogous Galactic thick disc and inner halo. find that GES merger is likely been gas-rich contribute 10-50$\%$ gas merger-induced centrally concentrated starburst results rapid compact, rotationally supported occupies typical chemical region abundance space. evidence mergers heated proto-disc Galaxy, scattering stars onto less-circular orbits such their rotation velocity metallicity positively correlate, thus contributing an additional connects demonstrate level kinematic heating proto-galaxy correlates with state population before merger, mass orbital eccentricity merger. Furthermore, we show time can be accurately inferred from local counter-rotating orbits.