SPIDER VIII - constraints on the stellar initial mass function of early-type galaxies from a variety of spectral features

By F. Barbera, I. Ferreras, A. Vazdekis, I. G. D. L. Rosa, R. D. Carvalho, M. Trevisan, J. Falc'on-Barroso, E. R. INAF-OAC, MSSL-UCL, Iac and 3 more. 2013

213 citations recorded by the source corpus.

We perform a spectroscopic study to constrain the stellar initial mass function (IMF) by using a large sample of 24 781 early-type galaxies from the Sloan Digital Sky Survey-based Spheroids Panchromatic Investigation in Different Environmental Regions survey. Clear evidence is found of a trend between IMF and central velocity dispersion (σ0), evolving from a standard Kroupa/Chabrier IMF at σ0 ~ 100 km s-1 towards a more bottom-heavy IMF with increasing σ0, becoming steeper than the Salpeter function at σ0 > 220 km s-1. We analyse a variety of spectral indices, combining gravity-sensitive features, with age- and metallicitysensitive indices, and we also consider the effect of non-solar abundance variations. The indices, corrected to solar scale by means of semi-empirical correlations, are fitted simultaneously with the (nearly solar-scaled) extended MILES (MIUSCAT) stellar population models. Similar conclusions are reached when analysing the spectra with a hybrid approach, combining constraints from direct spectral fitting in the optical with those from IMF-sensitive indices. Our analysis suggests that σ0, rather than [a/Fe], drives the variation of the IMF. Although our analysis cannot discriminate between a single power-law (unimodal) IMF and a low-mass (<0.5Mȯ) tapered (bimodal) IMF, robust constraints can be inferred for the fraction in lowmass stars at birth. This fraction (by mass) is found to increase from ~20 per cent at σ0 ~ 100 km s-1, up to ~80 per cent at σ0 ~ 300 km s-1. However, additional constraints can be provided with stellar mass-to-light (M/L) ratios: unimodal models predict M/L significantly larger than dynamical M/L, across the whole σ0 range, whereas a bimodal IMF is compatible. Our results are robust against individual abundance variations. No significant variation is found in Na and Ca in addition to the expected change from the correlation between [s-1/Fe] and σ0. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/36f71f5eb117b1844995274fd5c127273bcfb6bd

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Citations in the corpus

A unified multiwavelength model of galaxy formation (2015, background): “Several such studies (e.g. Conroy & van Dokkum 2012; La Barbera et al. 2013) find evidence for a bottom-heavy IMF in high mass galaxies.”
Radial variations in the stellar initial mass function of early-type galaxies (2014, background): “…previous studies suggested a trend with galaxy mass on a global sense (Cenarro et al. 2003; van Dokkum & Conroy 2010; Ferreras et al. 2013; La Barbera et al. 2013), our findings imply that it is in the cores of massive galaxies where star formation processes are fundamentally different,…”
UV-extended E-MILES stellar population models: young components in massive early-type galaxies (2016, background): “A bottom-heavy IMF, as recently claimed for massive early-type galaxies (e.g., La Barbera et al. 2013; Spiniello et al. 2014), decreases the Mg 2800 index by only ∼ 1Å for an SSP with a bimodal IMF with slope 2.8, which is clearly insufficient for matching the observed index values of these…”
OVERVIEW OF THE SDSS-IV MaNGA SURVEY: MAPPING NEARBY GALAXIES AT APACHE POINT OBSERVATORY (2014, background): “…state-of-the-art dynamical modeling (e.g, Cappellari et al. 2006; Cappellari 2008; van den Bosch et al. 2008; de Lorenzi et al. 2009; Long & Mao 2010) and IMF-sensitive spectrophotometric modeling (e.g., Conroy & van Dokkum 2012b; La Barbera et al. 2013; Spiniello et al. 2014) for the first time.”
A LINK BETWEEN STAR FORMATION QUENCHING AND INNER STELLAR MASS DENSITY IN SLOAN DIGITAL SKY SURVEY CENTRAL GALAXIES (2013, background): “Indeed, increasing evidence points to systematic variations in the IMF, such that steeper IMFs (more bottom-heavy) are inferred in (early-type) galaxies with higher velocity dispersions (e.g., Cappellari et al. 2012; Conroy & van Dokkum 2012; La Barbera et al. 2013).”
Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models (2015, methodology): “The reader should be warned, however, that neither TiO1 nor TiO2 show any significant variation with [Mg/Fe] in ETGs at fixed velocity dispersion (see La Barbera et al. 2013).”
Modelling and interpreting spectral energy distributions of galaxies with BEAGLE (2016, background): “…variations of the IMF, such as a potential steepening in early-type galaxies (e.g. van Dokkum & Conroy 2010; Conroy & van Dokkum 2012b; Cappellari et al. 2012; La Barbera et al. 2013; Sonnenfeld et al. 2015), for which theoretical motivations exist (e.g. Chabrier, Hennebelle & Charlot 2014).”