A substantial fraction of stars in clusters are not gravitationally bound to any particular galaxy. These stars constitute the so-called intracluster light (ICL). The ICL is distributed around the central galaxy of the cluster and extends to several hundred kpc away from the cluster center (e.g., Murante et al. 2004; Zibetti et al. 2005). This diffuse light is thought to form primarily by the tidal stripping of stars from galaxies that interact and merge during the hierarchical accretion history of the cluster (e.g., Gregg & West. 1998; Rudick et al. 2006; Conroy et al. 2007; Contini et al. 2014). Therefore, the characterization of the ICL provides a direct way of determining the assembly mechanisms occurring inside galaxy clusters. In this sense, the ICL is the signature of how violent the assembly of the cluster has been through its cosmic history. For that reason, it is absolutely key to determine how and when the ICL formed. However, the identification of this light observationally remains difficult and uncertain. Indeed, the typical surface brightness of the ICL is μV 26.5 mag arcsec−2 (e.g., Mihos et al. 2005; Zibetti et al. 2005; Rudick et al. 2006) and it is contaminated by foreground and background galaxies. Moreover, it is difficult to dissociate between the ICL and the brightest central galaxy surface brightness profile (e.g., Gonzalez et al. 2005; Krick et al. 2007).
Multiwavelength deep observations are a key tool to understand the origin of the ICL. For this reason, we take advantage of the Hubble Frontier Fields (HFF) survey to investigate the properties of the stellar populations of the ICL of its six massive intermediate redshift (0.3 < z < 0.6) clusters. We carry on this analysis down to a radial distance of ∼ 120 kpc from the brightest cluster galaxy. We found that the average metallicity of the ICL is [Fe/H]ICL ∼ − 0.5, compatible with the value of the outskirts of the MilkyWay. The mean stellar ages of the ICL are between 2 and 6 Gyr younger than the most massive galaxies of the clusters. Those results suggest that the ICL of these massive (> 10^15 Msol) clusters is formed by the stripping of MW-like objects that have been accreted at z< 1, in agreement with current simulations.We do not find any significant increase in the fraction of light of the ICL with cosmic time, although the redshift range explored is narrow to derive any strong conclusion. When exploring the slope of the stellar mass density profile, we found that the ICL of the HFF clusters follows the shape of their underlying dark matter haloes, in agreement with the idea that the ICL is the result of the stripping of galaxies at recent times.