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KINETyS: Constraining spatial variations of the stellar initial mass function in early-type galaxies

Alton, Padraig D.; Smith, Russell J.; Lucey, John R.

KINETyS: Constraining spatial variations of the stellar initial mass function in early-type galaxies Thumbnail


Authors

Padraig D. Alton

Profile image of John Lucey

John Lucey john.lucey@durham.ac.uk
Emeritus Professor



Abstract

The heavyweight stellar initial mass function (IMF) observed in the cores of massive early-type galaxies (ETGs) has been linked to formation of their cores in an initial swiftly quenched rapid starburst. However, the outskirts of ETGs are thought to be assembled via the slow accumulation of smaller systems in which the star formation is less extreme; this suggests that the form of the IMF should exhibit a radial trend in ETGs. Here, we report radial stellar population gradients out to the half-light radii of a sample of eight nearby ETGs. Spatially resolved spectroscopy at 0.8–1.35 μm from the Very Large Telescope's K-band Multi-Object Spectrograph instrument was used to measure radial trends in the strengths of a variety of IMF-sensitive absorption features (including some which are previously unexplored). We find weak or no radial variation in some of these which, given a radial IMF trend, ought to vary measurably, e.g. for the Wing–Ford band, we measure a gradient of +0.06 ± 0.04 per decade in radius. Using stellar population models to fit stacked and individual spectra, we infer that the measured radial changes in absorption feature strengths are primarily accounted for by abundance gradients, which are fairly consistent across our sample (e.g. we derive an average [Na/H] gradient of −0.53 ± 0.07). The inferred contribution of dwarf stars to the total light typically corresponds to a bottom-heavy IMF, but we find no evidence for radial IMF variations in the majority of our sample galaxies.

Citation

Alton, P. D., Smith, R. J., & Lucey, J. R. (2017). KINETyS: Constraining spatial variations of the stellar initial mass function in early-type galaxies. Monthly Notices of the Royal Astronomical Society, 468(2), 1594-1615. https://doi.org/10.1093/mnras/stx464

Journal Article Type Article
Acceptance Date Feb 21, 2017
Online Publication Date Feb 23, 2017
Publication Date Feb 23, 2017
Deposit Date May 8, 2017
Publicly Available Date May 9, 2017
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 468
Issue 2
Pages 1594-1615
DOI https://doi.org/10.1093/mnras/stx464
Public URL https://durham-repository.worktribe.com/output/1359489
Related Public URLs https://arxiv.org/abs/1702.05485

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Copyright Statement
This article has been published in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.






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