Chemical evolution of elliptical galaxies with a variable IMF

Abstract

Growing evidence in recent years suggests a systematic variation of the stellar initial mass function (IMF), being top-heavy for starburst galaxies and possibly bottom-heavy for massive ellipticals. Galaxy chemical evolution simulations adopting an invariant canonical IMF face difficulty in simultaneously reproducing the metallicity and α-enhancement of the massive elliptical galaxies. Applying a variable IMF that changes with time is a promising solution, however, it is non-trivial to couple a variable IMF theory with the existing galaxy evolution codes. Here we present the first open source simulation code which recalculates the galaxy-wide IMF at each time step according to the Integrated-Galactic-IMF (IGIMF) theory where the galaxy-wide IMF depends on the galactic star formation rate and metallicity. The resulting galaxy-wide IMF and metal abundance evolve with time. With this pilot work, we explore the effect of the IGIMF theory on galaxy chemical evolution in comparison with an invariant IMF.

Chemical evolution of ultra-faint dwarf galaxies in the self-consistently calculated integrated galactic IMF theory

“…In order to reproduce the observed properties of the UFD Boötes I, we used the GalIMF code 1 (Yan et al 2019) with 1 The code is publicly available at https://github.com/Azeret/ galIMF modifications to compute the galaxy mass, energy, and chemical evolution.…”

“…The chemical evolution of a dwarf galaxy is calculated using the galaxy chemical evolution model described in Yan et al (2019), applying most of the same assumptions as Lacchin et al (2020).…”

“…Here we describe the model modifications and initial settings for this particular study and refer to Yan et al (2019) for a detailed and comprehensive description of the galaxy chemical evolution model.…”

“…The premise of being able to place constraints on the smallscale empirical prescriptions entering the IGIMF formalism deserves further research. For this purpose, we used the publicly available chemical evolution code GalIMF (Yan et al 2019), the modular structure of which allows us to readily test different empirical prescriptions entering the IGIMF theory, thereby allowing us to study the chemical properties of UFDs in more detail.…”

The M dwarf problem: Fe and Ti abundances in a volume-limited sample of M dwarf stars

“…Some ⋆ E-mail: vwoolf@unomaha.edu alternatives to a simple model can produce better matches to the observed numbers of long-lived stars with different metallicities by abandoning one or more of its simplifying assumptions. Models have produced better matches to the observed metallicity trend by including inflow or outflow of material (Wyse & Gilmore 1995;Pagel 2001;Snaith et al 2015; Sánchez Almeida 2017), a varying IMF (Schmidt 1963;Carigi 1996;Martinelli & Matteucci 2000;Yan et al 2019), and/or variable star formation rates (Malinie et al 1993;Carigi 1996;Caimmi 2008).…”