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

De Masi, C., Vincenzo, F., Matteucci, F., Rosani, G., La Barbera, F., Pasquali, A. & Spitoni, E., Feb-2019, In : Monthly Notices of the Royal Astronomical Society. 483, 2, p. 2217-2235 19 p.

Research output: Contribution to journalArticleAcademicpeer-review

  • C. De Masi
  • F. Vincenzo
  • F. Matteucci
  • G. Rosani
  • F. La Barbera
  • A. Pasquali
  • E. Spitoni

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 [alpha/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. t(switch) = 0.1 Gyr.

Original languageEnglish
Pages (from-to)2217-2235
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume483
Issue number2
Publication statusPublished - Feb-2019

    Keywords

  • galaxies: abundances, galaxies: elliptical and lenticular, cD, galaxies: evolution, galaxies: formation, galaxies: luminosity function, mass function, INITIAL MASS FUNCTION, EARLY-TYPE GALAXIES, STELLAR POPULATION SYNTHESIS, PHOTOCHEMICAL EVOLUTION, SYSTEMATIC VARIATION, FUNDAMENTAL PLANE, DYNAMICAL MODELS, GALACTIC STELLAR, STAR-FORMATION, STRONG LENSES

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