The Fall of a Giant. Chemical evolution of Enceladus, alias the Gaia
  Sausage
  We present the first chemical evolution model for Enceladus, alias the Gaia
Sausage, to investigate the star formation history of one of the most massive
satellites accreted by the Milky Way during a major merger event. Our best
chemical evolution model for Enceladus nicely fits the observed stellar
[$\alpha$/Fe]-[Fe/H] chemical abundance trends, and reproduces the observed
stellar metallicity distribution function, by assuming low star formation
efficiency, fast infall time scale, and mild outflow intensity. We predict a
median age for Enceladus stars $12.33^{+0.92}_{-1.36}$ Gyr, and - at the time
of the merger with our Galaxy ($\approx10$ Gyr ago from Helmi et al.) - we
predict for Enceladus a total stellar mass $M_{\star} \approx 5 \times
10^{9}\,\text{M}_{\odot}$. By looking at the predictions of our best model, we
discuss that merger events between the Galaxy and systems like Enceladus may
have inhibited the gas accretion onto the Galaxy disc at high redshifts,
heating up the gas in the halo. This scenario could explain the extended period
of quenching in the star formation activity of our Galaxy about 10 Gyr ago,
which is predicted by Milky Way chemical evolution models, in order to
reproduce the observed bimodality in [$\alpha$/Fe]-[Fe/H] between thick- and
thin-disc stars.
