Inferring the dark matter distribution of massive galaxy clusters from deep optical observations: insights from the TNG300 simulation

Extragalactic stars within galaxy clusters contribute to the intracluster light (ICL), which is thought to be a promising tracer of the underlying dark matter (DM) distribution. In this study, we employ the TNG300 simulation to investigate the prospect of recovering the dark matter distribution of galaxy clusters from deep, wide-field optical images. For this, we generate mock observations of 40 massive clusters (M₂₀₀ 1014.5\, M_) at $z=0.06$ for the $g'$ band of the Wendelstein Wide-Field Imager (WWFI), and isolate the emission from the brightest cluster galaxy (BCG) and the ICL by masking the satellite galaxies, following observational procedures. By comparing ΣBCG+ICL profiles from these images against ΣDM profiles for the central subhaloes, we find that Σcen-DM/ΣBCG+ICL exhibits a quasi-linear scaling relation in log space with the normalised distance r/R_Δ, for both R_Δ=R₂₀₀ and R₅₀₀. The scatter in the scaling is predominantly stochastic, showing a weak dependence on formation time and dynamical state. We recover the DM concentration and mass within ≈ 23 and ≈ 15 per cent of their true values (for R₂₀₀), respectively, and with ≈ 3 per cent larger uncertainties for R₅₀₀. Alternatively, we find that the concentration can be estimated using the BCG+ICL fraction, the central's DM mass using the BCG+ICL flux, and the total DM mass using the bolometric flux. These results demonstrate the feasibility of deriving dark matter characteristics of galaxy clusters to be observed with facilities like the Vera C. Rubin Observatory in the near future.