Further evidence for a time-dependent initial mass function in massive early-type galaxies

Abstract

Spectroscopic analyses of gravity-sensitive line strengths give growing evidence towards an excess of low-mass stars in massive early-type galaxies (ETGs). Such a scenario requires a bottom-heavy initial mass function (IMF). However, strong constraints can be imposed if we take into account galactic chemical enrichment. We extend the analysis of Weidner et al. and consider the functional form of bottom-heavy IMFs used in recent works, where the high-mass end slope is kept fixed to the Salpeter value, and a free parameter is introduced to describe the slope at stellar masses below some pivot mass scale (M<MP=0.5Msun). We find that no such time-independent parameterisation is capable to reproduce the full set of constraints in the stellar populations of massive ETGs - resting on the assumption that the analysis of gravity-sensitive line strengths leads to a mass fraction at birth in stars with mass M<0.5Msun above 60%. Most notably, the large amount of metal-poor gas locked in low-mass stars during the early, strong phases of star formation results in average stellar metallicities [M/H]<-0.6, well below the solar value. The conclusions are unchanged if either the low-mass end cutoff, or the pivot mass are left as free parameters, strengthening the case for a time-dependent IMF.

5 pages, 4 figures, 1 table. MNRAS Letters, in press

References in corpus (33)

• Galactic Stellar and Substellar Initial Mass Function
• On the variation of the Initial Mass Function
• The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems
• The epochs of early-type galaxy formation as a function of environment
• The Stellar Population Histories of Early-Type Galaxies. II. Controlling Parameters of the Stellar Populations
• A systematic variation of the stellar initial mass function in early-type galaxies
• A Substantial Population of Low Mass Stars in Luminous Elliptical Galaxies
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. II. Results
• A new chemo-evolutionary population synthesis model for early-type galaxies. I: Theoretical basis
• Evidence for top-heavy stellar initial mass functions with increasing density and decreasing metallicity
• SPIDER VIII - Constraints on the Stellar Initial Mass Function of Early-type Galaxies from a Variety of Spectral Features
• Evidence for a Non-Uniform Initial Mass Function in the Local Universe
• Galaxy And Mass Assembly (GAMA): The star formation rate dependence of the stellar initial mass function
• Systematic variation of the stellar Initial Mass Function with velocity dispersion in early-type galaxies
• A new chemo-evolutionary population synthesis model for early-type galaxies. II: Observations and Results
• Near-IR line-strengths in elliptical galaxies: evidence for IMF variations?
• Evidence for a non-universal stellar initial mass function from the integrated properties of SDSS galaxies
• Variations of the stellar initial mass function in the progenitors of massive early-type galaxies and in extreme starburst environments
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. I. Data and Empirical Trends
• Variations in the initial mass function in early-type galaxies: A critical comparison between dynamical and spectroscopic results
• A giant elliptical galaxy with a lightweight initial mass function
• Low-mass X-ray binaries indicate a top-heavy stellar initial mass function in ultra compact dwarf galaxies
• The (galaxy-wide) IMF in giant elliptical galaxies: From top to bottom
• The link between the Star Formation History and [alpha/Fe]
• Variations in the Stellar IMF: from Bottom to Top
• A low-mass cut-off near the hydrogen burning limit for Salpeter-like initial mass functions in early-type galaxies
• Testing the universal stellar IMF on the metallicity distribution in the bulges of the Milky Way and M31
• Bottom-heavy initial mass function in a nearby compact L*-galaxy
• Probing the evolution of early-type cluster galaxies through chemical enrichment
• On breaking the age-metallicity degeneracy in early-type galaxies: Outflows versus Star Formation Efficiency
• The near-IR Ca II triplet - sigma relation for bulges of spiral galaxies
• Origin of a bottom-heavy stellar initial mass function in elliptical galaxies
• The star-formation histories of elliptical galaxies across the fundamental plane

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