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 \upmu m and 2.26 \upmu m features , the Na I 2.21 \upmu m line , and the CO 2.30 \upmu m 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 \pm 0.05 per dex in fractional radius and an average [ Na/Fe ] gradient of –0.35 \pm 0.09 .
We find a large but radially-constant enhancement to [ Mg/Fe ] of \sim 0.4 and a much lower [ Ca/Fe ] enhancement of \sim 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 ) .