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Title: Origin of a bottom-heavy stellar initial mass function in elliptical galaxies

We investigate the origin of a bottom-heavy stellar initial mass function (IMF) recently observed in elliptical galaxies by using chemical evolution models with a non-universal IMF. We adopt the variable Kroupa IMF with the three slopes (α{sub 1}, α{sub 2}, and α{sub 3}) dependent on metallicities ([Fe/H]) and densities (ρ{sub g}) of star-forming gas clouds and thereby search for the best IMF model that can reproduce (1) the observed steep IMF slope (α{sub 2} ∼ 3, i.e., bottom-heavy) for low stellar masses (m ≤ 1 M {sub ☉}) and (2) the correlation of α{sub 2} with chemical properties of elliptical galaxies in a self-consistent manner. We find that if the IMF slope α{sub 2} depends on both [Fe/H] and ρ{sub g}, then elliptical galaxies with higher [Mg/Fe] can have steeper α{sub 2} (∼3) in our models. We also find that the observed positive correlation of stellar mass-to-light ratios (M/L) with [Mg/Fe] in elliptical galaxies can be quantitatively reproduced in our models with α{sub 2}∝β[Fe/H] + γlog ρ{sub g}, where β ∼ 0.5 and γ ∼ 2. We discuss whether the IMF slopes for low-mass (α{sub 2}) and high-mass stars (α{sub 3}) need to vary independently from each other to explainmore » a number of IMF-related observational results self-consistently. We also briefly discuss why α{sub 2} depends differently on [Fe/H] in dwarf and giant elliptical galaxies.« less
Authors:
 [1]
  1. ICRAR, M468, The University of Western Australia, 35 Stirling Highway, Crawley Western Australia 6009 (Australia)
Publication Date:
OSTI Identifier:
22348567
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CORRELATIONS; DENSITY; EVOLUTION; GALAXIES; MASS; METALLICITY; STARS; VISIBLE RADIATION