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

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  • stv357

    Final published version, 1.45 MB, PDF document

  • Fiorenzo Vincenzo
  • Francesca Matteucci
  • Simone Recchi
  • Francesco Calura
  • Andrew McWilliam
  • Gustavo A. Lanfranchi
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Original languageEnglish
Article numberstv357
Pages (from-to)1327-1339
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume449
Issue2
Early online date23 Mar 2015
DOIs
Publication statusPublished - 11 May 2015

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.

Notes

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved

ID: 11927566