Radial Gradients and Intrinsic Scatter in MaNGA Galaxies

Abstract We derive stellar population parameters and radial gradients within 0.65 R e for spatially resolved spectra of 2968 early-type galaxies from MaNGA, spanning stellar velocity dispersions ( σ ) of 50–340 km s −1 . Light-weighted mean age, C, N, Na, Mg, and Fe abundances are obtained by inverting metallicity-composite stellar population models with isochrones that respond in T eff to individual element abundance changes. Globally, log age increases (∼0.53 dex per decade), [Fe/H] declines slightly (∼–0.06 dex per decade), and [X/Fe] for light elements rises (0.19–0.37 dex per decade for log σ < 2.0 but steepens to nearly double slope for log σ > 2.0) with log σ . [Fe/H] peaks at log σ ≈ 2.0 and falls on either side. Light element [X/Fe] anticorrelates with [Fe/H] (∼–0.1 dex per decade). Astrophysical scatter is largest in low- σ galaxies, especially for Fe and N. Internally, age gradients are nearly flat in low- σ galaxies and slightly negative in high- σ systems (∼–0.04 dex per decade). [Fe/H] radial gradients steepen from −0.06 dex per decade to –0.15 dex per decade across σ , while light elements (except Na) show ∼–0.03 dex per decade gradients. Scatter in gradients peaks in high- σ galaxies, most strongly for Fe (∼0.23 dex), suggesting comparable numbers of inside-out and outside-in formation. A near-zero (∼–0.03) age and light-element gradient plus mild [Fe/H] gradients supports hierarchical merging for ETG evolution. Simulations match the observed age structure, slope change at log σ ≈ 2.0, and flat gradients, though they overpredict absolute abundances.