The IGIMF and other IMFs in dSphs: the case of Sagittarius

Fiorenzo Vincenzo, Francesca Matteucci, Simone Recchi, Francesco Calura, Andrew McWilliam, Gustavo A. Lanfranchi

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    15 Citations (Scopus)
    26 Downloads (Pure)

    Abstract

    We have studied the effects of various initial mass functions (IMFs) on the chemical evolution
    of the Sagittarius dwarf galaxy (Sgr). In particular, we tested the effects of the integrated galactic
    initial mass function (IGIMF) on various predicted abundance patterns. The IGIMF depends
    on the star formation rate and metallicity and predicts less massive stars in a regime of low
    star formation, as it is the case in dwarf spheroidals. We adopted a detailed chemical evolution
    model following the evolution of α-elements, Fe and Eu, and assuming the currently best set of
    stellar yields. We also explored different yield prescriptions for the Eu, including production
    from neutron star mergers. Although the uncertainties still present in the stellar yields and data
    prevent us from drawing firm conclusions, our results suggest that the IGIMF applied to Sgr
    predicts lower [α/Fe] ratios than classical IMFs and lower [hydrostatic/explosive] α-element
    ratios, in qualitative agreement with observations. In our model, the observed high [Eu/O]
    ratios in Sgr is due to reduced O production, resulting from the IGIMF mass cut-off of the
    massive oxygen-producing stars, as well as to the Eu yield produced in neutron star mergers,
    a more promising site than core-collapse supernovae, although many uncertainties are still
    present in the Eu nucleosynthesis. We find that a model, similar to our previous calculations,
    based on the late addition of iron from the Type Ia supernova time-delay (necessary to reproduce
    the shape of [X/Fe] versus [Fe/H] relations) but also including the reduction of massive
    stars due to the IGIMF, better reproduces the observed abundance ratios in Sgr than models
    without the IGIMF.
    Original languageEnglish
    Article numberstv357
    Pages (from-to)1327-1339
    Number of pages13
    JournalMonthly Notices of the Royal Astronomical Society
    Volume449
    Issue number2
    Early online date23 Mar 2015
    DOIs
    Publication statusPublished - 11 May 2015

    Keywords

    • stars: abundances
    • galaxies: abundances
    • galaxies: dwarf
    • galaxies: evolution
    • galaxies: formation
    • Local Group

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