The fall of a giant. Chemical evolution of Enceladus, alias the Gaia sausage

Research output: Contribution to journalArticle


  • Emanuele Spitoni
  • Francesco Calura
  • Francesca Matteucci
  • Victor Silva Aguirre
  • Gabriele Cescutti

Colleges, School and Institutes


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 [α/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 (≈10 Gyr ago from Helmi et al.) – we predict for Enceladus a total stellar mass M⋆ ≈ 5 × 109 M. 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 on to 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 [α/Fe]–[Fe/H] between thick- and thin-disc stars.

Bibliographic note

Accepted for publication in MNRAS Letters


Original languageEnglish
Pages (from-to)L47–L52
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date14 May 2019
Publication statusPublished - 1 Jul 2019


  • astro-ph.GA, stars: abundances, Galaxy: abundances, Galaxy: evolution, Galaxy: formation, galaxies: individual: Enceladus, galaxies: individual: Gaia Sausage