The Fall of a Giant. Chemical evolution of Enceladus, alias the Gaia Sausage

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  • Fiorenzo Vincenzo, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
  • ,
  • Emanuele Spitoni
  • Francesco Calura, INAF, Osservatorio Astronomico di Bologna, Via Gobetti 93/3, I-40129 Bologna, Italy 0000-0002-6175-0871
  • ,
  • Francesca Matteucci, INFN, Sezione di Trieste, Via Valerio 2, I-34100 Trieste, Italy
  • ,
  • Victor Silva Aguirre
  • Andrea Miglio, School of Physics and Astronomy, University of Birmingham, Edgbaston Park Road, West Midlands, Birmingham, B15 2TT UK 0000-0001-5998-8533
  • ,
  • Gabriele Cescutti, INAF, Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, I-34131 Trieste, Italy 0000-0002-3184-9918
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\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 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.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society: Letters
Publication statusPublished - 1 Jul 2019
Externally publishedYes

    Research areas

  • stars: abundances, Galaxy: abundances, Galaxy: evolution, Galaxy: formation, galaxies: individual: Enceladus, galaxies: individual: Gaia Sausage

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