University of Hertfordshire

From the same journal

From the same journal

Is the IMF in ellipticals bottom-heavy? Clues from their chemical abundances

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  • sty3127

    Final published version, 9.36 MB, PDF document

  • C. De Masi
  • F. Vincenzo
  • F. Matteucci
  • G. Rosani
  • La Barbera
  • A. Pasquali
  • E. Spitoni
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Original languageEnglish
Article numbersty3127
Pages (from-to)2217–2235
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Early online date22 Nov 2018
Publication statusPublished - Feb 2019


We tested the implementation of different initial mass functions (IMFs) in our model for the chemical evolution of ellipticals, with the aim of reproducing the observed relations of [Fe/H] and [Mg/Fe] abundances with galaxy mass in a sample of early-type galaxies selected from the SPIDER-SDSS catalogue. Abundances in the catalogue were derived from averaged spectra, obtained by stacking individual spectra according to central velocity dispersion, as a proxy of galaxy mass. We tested IMFs already used in a previous work, as well as two new models, based on low-mass tapered (‘bimodal’) IMFs, where the IMF becomes either (1) bottom-heavy in more massive galaxies, or (2) is time-dependent, switching from top-heavy to bottom-heavy in the course of galactic evolution. We found that observations could only be reproduced by models assuming either a constant, Salpeter IMF, or a time-dependent distribution, as other IMFs failed. We further tested the models by calculating their M/L ratios. We conclude that a constant, time-independent bottom-heavy IMF does not reproduce the data, especially the increase of the [α/Fe] ratio with galactic stellar mass, whereas a variable IMF, switching from top to bottom-heavy, can match observations. For the latter models, the IMF switch always occurs at the earliest possible considered time, i.e. tswitch = 0.1 Gyr.


© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.

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