Radial abundance gradients of 18 elements in Galactic open clusters from infrared MWM spectra A detailed analysis of 655 giants in 133 clusters

Abstract

Open clusters are powerful tools for studying the Milky Way. While large spectroscopic surveys now provide spectra for many cluster members, automated pipelines and heterogeneous membership selections can introduce systematics and inflate apparent cluster scatter. Therefore, a homogeneous re-analysis with careful membership control and an explicit treatment of departures from Local Thermodynamic Equilibrium is valuable for establishing robust abundance gradients. The aim is to derive precise Galactic radial abundance gradients for multiple elements using open cluster giants, and to investigate how these gradients depend on cluster age. We re-analysed high-resolution infrared APOGEE Milky Way Mapper spectra from DR19 of the Sloan Digital Sky Survey for 655 open cluster members selected from Gaia data that satisfied strict quality cuts on signal-to-noise ratio. Stellar parameters and 18 elemental abundances were obtained using spectrum fitting with the Python version of Spectroscopy Made Easy, applying Non-Local Thermodynamic Equilibrium corrections for several key atomic species. Further quality control of the results was made by visual inspection of all fitted synthetic spectra. The metallicity of the clusters decreases with Galactocentric radius, following a global slope close to -0.06 dex/kpc. Beyond 10-11 kpc, there is modest flattening. In addition to the elements analysed in the \cite{otto2026} study, we derive open-cluster gradients for V, Cu, Zn and Yb using APOGEE spectra.