The Buildup of the Intracluster Light of A85 as Seen by Subaru's Hyper Suprime-Cam

The study of low surface brightness light in large, deep imaging surveys is still uncharted territory as automated data reduction pipelines over-subtract or eliminate this light. Using archival data of the A85 cluster of galaxies taken with the Hyper Suprime-Cam on the Subaru Telescope, we show that using careful data processing can unveil the diffuse light within the cluster, the intracluster light. We reach surface brightness limits of ${\mu }_g^{limit}$(3σ, 10″ × 10″) = 30.9 and ${\mu }_i^{limit}$(3σ, 10″ × 10″) = 29.7 mag arcsec⁻². We measured the radial surface brightness profiles of the brightest cluster galaxy out to the intracluster light (radius ∼215 kpc) for the g and i bands. We found that both the surface brightness and the color profiles become shallower beyond ∼75 kpc suggesting that a distinct component, the intracluster light, starts to dominate at that radius. The color of the profile at ∼100 kpc suggests that the buildup of the intracluster light of A85 occurs by the stripping of massive (∼10¹⁰ M _⊙) satellites. The measured fraction of this light ranges from 8%–30% in g, depending on the definition of intracluster light chosen.