A new era of intracluster light studies with JWST

Abstract

Still largely unexplored, the diffuse light in cluster of galaxies traces the past and on-going buildup of these massive structures. Here, we present the first comprehensive study of the intracluster light (ICL) of the cluster SMACS-J0723.3-7327 (z=0.39) using the JWST Early Release Observations. These deep and high spatial resolution images allow the study of the ICL with high signal-to-noise ratio up to a radial distance of $\sim400$ kpc, twice as far with respect to previous HST studies of intermediate redshift clusters. This opens up the possibility of exploring the rich mixture of processes that are building the ICL. We find that the inner parts (R$<$100 kpc) are built through a major merger while the outer parts (R$>$ 100 kpc) are mainly produced by the tidal stripping of Milky Way-like satellites. We also found that the slope of the stellar mass density radial profile of the ICL of this cluster ($\alpha_{3D} = -2.47\pm0.13$) follows closely the predicted dark matter halo slope ($\alpha_{3D\mathrm{,DM}} = -2.6$ to $-2$), supporting the idea that both components have a similar shape and thus the potential of using the ICL as a tracer of the dark matter distribution in clusters of galaxies. Future JWST studies of the ICL are set to revolutionise our understanding of cluster formation and will be crucial to improve the gravitational lensing mass maps of these structures and thus to accurately characterise the properties of the first galaxies.