Euclid: Early Release Observations - The intracluster light of Abell 2390

The intracluster light (ICL) provides a record of the dynamical interactions undergone by clusters, giving clues on cluster formation and evolution.Here, we analyse the properties of ICL in the massive cluster Abell 2390 at redshift z = 0.228. Our analysis is based on the deep images obtainedby the Euclid mission as part of the Early Release Observations in the near-infrared (YE, JE, HE bands), using the NISP instrument in a 0.5 deg2field. We subtracted a PSF model and removed the Galactic cirri contribution in each band after modelling it with the DAWIS software. We thenapplied three methods to detect, characterise and model the ICL and the brightest cluster galaxy (BCG): the CICLE 2D multi-galaxy fitting, theDAWIS wavelet-based multiscale software, and a mask-based 1D profile fitting. We detect ICL up to 600 kpc. The ICL fractions derived by ourthree methods range between 18 % and 36 % (average of 24 %), while the BCG+ICL fractions are between 21 % and 41 % (average of 26 %),depending on the band and method. A galaxy density map based on 219 selected cluster members shows a strong substructure to the south-eastand a smaller one to the north-west. Ellipticals dominate in the cluster’s central region, with a centroid offset from the BCG by about 70 kpc,and a distribution following that of the ICL. The comparison of the BCG+ICL, mass from gravitational lensing, and X-ray maps show that theBCG+ICL traces better substructures in the cluster. Based on colours, the ICL (out to ∼ 400 kpc) seems to be built by the accretion of smallsystems (M ∼ 109.5M⊙), or from stars coming from the outskirts of Milky Way-type galaxies (M ∼ 1010M⊙). Though Abell 2390 does not seemto be undergoing a merger, it is not yet fully relaxed, since it has accreted two groups that have not yet fully merged with the cluster core. Weestimate that the contributions to the inner 300 kpc of the ICL of the north-west and south-east subgroups are 21 % and 9 % respectively.Key words. Galaxies: clusters: individual: Abell 2390, Galaxies: clusters: intracluster medium, Galaxies: individual: