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

ABSTRACT 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 DM distribution of galaxy clusters from deep wide-field optical images. For this, we generate mock observations of 40 massive clusters ($M_{200}\gtrsim 10^{14.5}\, {\rm M}_\odot$) at $z=0.06$ for the $g^{\prime }$ band of the Wendelstein Wide-Field Imager, and isolate the emission from the brightest cluster galaxy (BCG) and the ICL by masking the satellite galaxies, following observational procedures. By comparing $\Sigma _{\rm BCG+ICL}$ profiles from these images against $\Sigma _{\rm DM}$ profiles for the central subhaloes, we find that $\Sigma _{\rm cen-DM}/\Sigma _{\rm BCG+ICL}$ exhibits a quasi-linear scaling relation in log space with the normalized distance $r/R_{\Delta }$, for both $R_{\Delta }=R_{200}$ and $R_{500}$. 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 $\approx 23$ and $\approx 15$ per cent of their true values (for $R_{200}$), respectively, and with $\approx 3$ per cent larger uncertainties for $R_{500}$. 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 DM characteristics of galaxy clusters to be observed with facilities like the Vera C. Rubin Observatory in the near future.