Systematic variation of the stellar initial mass function with velocity dispersion in early-type galaxies

By I. Ferreras, F. Barbera, R. D. Carvalho, I. G. D. L. Rosa, A. Vazdekis, J. Falc'on-Barroso, E. Ricciardelli. 2012

177 citations recorded by the source corpus.

An essential component of galaxy formation theory is the stellarinitial mass function (IMF) that describes the parent distribution ofstellar mass in star-forming regions. We present observational evidence in a sample of early-type galaxies (ETGs) of a tight correlation between central velocity dispersion and the strength of several absorption features sensitive to the presence of low-mass stars. Our samplecomprises ~40 000 ETGs from the Spheroids Panchromatic Investigation in Different Environmental Regions survey (z ∼ 0.1). The data-extracted from the Sloan Digital Sky Survey-are combined, rejecting both noisy data, and spectra with contamination from telluric lines, resulting in a set of 18 stacked spectra at high signal-to-noise ratio (S/N ≳ 400a-1). A combined analysis of IMF-sensitive line strengths and spectral fitting is performed with the latest state-of-the-art population synthesis models (an extended version of the MILES models). Asignificant trend is found between IMF slope and velocity dispersion, towards an excess of low-mass stars in the most massive galaxies. Although we emphasize that accurate values of the IMF slope will requirea detailed analysis of chemical composition (such as [α/Fe] or even individual element abundance ratios), the observed trends suggest thatlow-mass ETGs are better fitted by a Kroupa-like IMF, whereas massivegalaxies require bottom-heavy IMFs, exceeding the Salpeter slope at σ ≳ 200 km s-1. © 2012 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/c7b0e7ee25b539202f49a0af8c7c0b97a80f2059

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In Astronomy and Astrophysics

1. M. Cappellari
2. C. Conroy
3. T. Naab
4. P. Hopkins
5. M. Sarzi
6. Eric Emsellem
7. L. Hernquist
8. J. Falc'on-Barroso

Citations in the corpus

• Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, methodology): “…of the studies used IMF sensitive spectral features in combination with stellar population models (e.g. van Dokkum & Conroy 2012; Conroy & van Dokkum 2012b; Spiniello et al. 2012; Smith et al. 2012a; Ferreras et al. 2013; Spiniello et al. 2015; La Barbera et al. 2015; Mart́ın-Navarro et al. 2015b).”
• Dusty Star Forming Galaxies at High Redshift (2014, background): “…so called ‘‘Wing-Ford’’ band; Ca II and Na I) aimed at distinguishing K and M dwarfs from K and M giants have found the IMF to be bottom heavy in z ∼ 0 early type galaxies (van Dokkum and Conroy, 2010; van Dokkum, 2012; Conroy and vanDokkum, 2012a,b; Spiniello et al., 2012; Ferreras et al., 2013).”
• The ATLAS3D project – XX. Mass–size and mass–σ distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function (2012, background): “Our trend with σ e is also smaller than the one reported by Ferreras et al. (2013) from spectral analysis, who find a rapid change from a Kroupa to a Salpeter IMF in the narrow interval σ ≈ 150–200 km s−1.”
• THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT (2013, unknown): “Correlation of IMF slope with galactic velocity dispersion has been shown via spectroscopic line widths (van Dokkum & Conroy 2011; Conroy & van Dokkum 2012; Ferreras et al. 2013), fundamental plane relations (Cappellari et al. 2012a; Dutton et al. 2012) and gravitational lensing (Treu et al. 2010).”
• Galaxy Masses: A Review (2013, background): “…possible variations with morphology or other parameters (e.g. Dutton et al. 2012; Conroy & van Dokkum 2012; Conroy et al. 2013; Sonnenfeld et al. 2012; Spiniello et al. 2011, 2012, 2013; Smith & Lucey 2013; Ferreras et al. 2013; Goudfrooij & Kruijssen 2013, and elsewhere in this review).”
• Radial variations in the stellar initial mass function of early-type galaxies (2014, background): “…of the IMF is driven by an increase of the fraction of dwarf-to-giant stars, i.e. a change towards steeper IMF slopes with higher velocity dispersion (Cenarro et al. 2003; Falcón-Barroso et al. 2003; Cappellari et al. 2012; Ferreras et al. 2013; La Barbera et al. 2013, hereafter LB13).”
• SPIDER VIII - constraints on the stellar initial mass function of early-type galaxies from a variety of spectral features (2013, methodology): “Following our previous work (Ferreras et al. 2013, hereafter FLD13), we further limit the analysis to objects (NETGs = 33, 095) with low internal extinction, i.e. a colour excess E(B − V ) < 0.1 mag 3.”
• The stellar IMF in early-type galaxies from a non-degenerate set of optical line indices (2013, background): “Ferreras et al. (2013) also found a correlation between c© 2002 RAS, MNRAS 000, 1–15 central velocity-dispersion and IMF slope for a large sample of SDSS ETGs.”
• Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models (2015, result): “It is worth noting that the very low-mass (VLM) (<0.6 M ) tapered ‘bimodal’ IMF has been found to be consistent with the line strengths and M/L of massive ETGs (e.g. Ferreras et al. 2013; La Barbera et al. 2013; Spiniello et al. 2014).”
• Mapping stellar content to dark matter haloes using galaxy clustering and galaxy–galaxy lensing in the SDSS DR7 (2015, background): “…galaxies above 3 × 1011h−2M may be underes- 1 http://home.strw.leidenuniv.nl/˜jarle/SDSS/ 2 For evidence suggesting non-universal IMFs, however, see van Dokkum & Conroy (2010), Conroy & van Dokkum (2012), Cappellari et al. (2012), and Ferreras et al. (2013). timated by as much as a factor of five.”