KINETyS II: Constraints on spatial variations of the stellar initial mass function from K-band spectroscopy

Alton, P.D.; Smith, R.J.; Lucey, J.R.

Abstract

We investigate the spatially resolved stellar populations of a sample of seven nearby massive Early-type galaxies (ETGs), using optical and near infrared data, including K-band spectroscopy. This data offers good prospects for mitigating the uncertainties inherent in stellar population modelling by making a wide variety of strong spectroscopic features available. We report new VLT-KMOS measurements of the average empirical radial gradients out to the effective radius in the strengths of the Ca I 1.98 μm and 2.26 μm features, the Na I 2.21 μm line, and the CO 2.30 μm bandhead. Following previous work, which has indicated an excess of dwarf stars in the cores of massive ETGs, we pay specific attention to radial variations in the stellar initial mass function (IMF) as well as modelling the chemical abundance patterns and stellar population ages in our sample. Using state-of-the-art stellar population models we infer an [Fe/H] gradient of –0.16±0.05 per dex in fractional radius and an average [Na/Fe] gradient of –0.35±0.09. We find a large but radially-constant enhancement to [Mg/Fe] of ∼ 0.4 and a much lower [Ca/Fe] enhancement of ∼ 0.1. Finally, we find no significant IMF radial gradient in our sample on average and find that most galaxies in our sample are consistent with having a Milky Way-like IMF, or at most a modestly bottom heavy IMF (e.g. less dwarf enriched than a single power law IMF with the Salpeter slope).

Citation

Alton, P., Smith, R., & Lucey, J. (2018). KINETyS II: Constraints on spatial variations of the stellar initial mass function from K-band spectroscopy. Monthly Notices of the Royal Astronomical Society, 478(4), 4464-4486. https://doi.org/10.1093/mnras/sty1242

• Journal Article Type: Article
• Acceptance Date: May 4, 2018
• Online Publication Date: May 14, 2018
• Publication Date: Aug 21, 2018
• Deposit Date: May 18, 2018
• Publicly Available Date: May 18, 2018
• 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: 478
• Issue: 4
• Pages: 4464-4486
• DOI: https://doi.org/10.1093/mnras/sty1242
• Public URL: https://durham-repository.worktribe.com/output/1325998
• Related Public URLs: https://arxiv.org/abs/1805.05964