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Calibrated, cosmological hydrodynamical simulations with variable IMFs - II. Correlations between the IMF and global galaxy properties

Barber, C, Schaye, J and Crain, RA (2018) Calibrated, cosmological hydrodynamical simulations with variable IMFs - II. Correlations between the IMF and global galaxy properties. Monthly Notices of the Royal Astronomical Society, 482 (2). pp. 2515-2529. ISSN 0035-8711

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Abstract

The manner in which the stellar initial mass function (IMF) scales with global galaxy properties is under debate. We use two hydrodynamical, cosmological simulations to predict possible trends for two self-consistent variable IMF prescriptions that, respectively, become locally bottom-heavy or top-heavy in high-pressure environments. Both simulations have been calibrated to reproduce the observed correlation between central stellar velocity dispersion and excess mass-to-light ratio (MLE) relative to a Salpeter IMF by increasing the mass fraction of, respectively, dwarf stars or stellar remnants. We find trends of MLE with galaxy age, metallicity, and [Mg/Fe] that agree qualitatively with observations. Predictions for correlations withexces luminosity, half-light radius, and black hole (BH) mass are presented. The significance of many of these correlations depends sensitively on galaxy selection criteria such as age, luminosity, and morphology. For an IMF with a varying high-mass end, some of these correlations are stronger than the correlation with the birth interstellar medium pressure (the property that governs the form of the IMF) because in this case the MLE has a strong age dependence. Galaxies with large MLE tend to have overmassive central BHs. This indicates that the abnormally high MLE observed in the centres of some high-mass galaxies does not imply that overmassive BHs are merely the result of incorrect IMF assumptions, nor that excess M/L ratios are solely the result of overmassive BHs. Satellite galaxies tend to scatter towards high MLE due to tidal stripping, which may have significant implications for the inferred stellar masses of ultracompact dwarf galaxies.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 16 Jan 2019 11:39
Last Modified: 16 Jan 2019 11:47
DOI or Identification number: 10.1093/mnras/sty2825
URI: http://researchonline.ljmu.ac.uk/id/eprint/9956

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