2026ApJ...997..109B

Observed metal abundances in the intracluster medium (ICM) of galaxy groups and clusters, Z_ICM, exceed what is expected from present-day stellar populations alone. Galaxy clusters are presumed to be near closed-box systems, allowing constraints to be placed on the origins of metals and stellar populations responsible for Z_ICM. We present a uniform XMM-Newton survey of 26 galaxy groups and clusters, measuring radial metallicity profiles and relating Z_ICM with the stellar fraction M_*/M_gas. We determine Z_ICM via spectral fitting across multiple annuli, finding a best fit of ${Z}_{\mathrm{ICM}}=-0.0{8}_{-0.07}^{+0.07}\,{\mathrm{log}}\left(\tfrac{{M}_{* }}{{M}_{\mathrm{gas}}}\right)+0.3{0}_{-0.06}^{+0.06}$ with intrinsic scatter ${\sigma }_{p}=0.0{9}_{-0.01}^{+0.02}$. We use closed-box chemical evolution models to estimate the metallicity yield from observable stellar populations, incorporating updated supernova yields and corrections for metals locked in remnants, ${Z}_{* }=(1.14\pm 0.52)\,{\mathrm{log}}\left(1+\tfrac{{M}_{* }}{{M}_{\mathrm{gas}}}\right)$. Our results demonstrate that present-day stellar populations systematically underpredict Z_ICM, with an inferred excess component increasing in systems with low M_*/M_gas. This trend supports the need for an early enrichment population (EEP) distinct from visible stars, Z_EEP. We find this necessity holds when reconsidering the closed-box assumption by removing all galaxy groups, potential leaky systems, deriving Z_EEP within 1σ when including and excluding groups. Three systems (NGC 1132, NGC 5098, and NGC 4325) deviate from the survey trend, exhibiting steep negative radial metallicity gradients and unusually low Z_ICM. We posit these systems to be late forming, whose ICM enrichment reflects only recent stellar populations. Our analysis quantifies the necessity of an EEP and provides trends for testing cluster chemical evolution models.