Multiscale exploration of SMACS J0723.3--7327's intracluster light and past dynamical history

Abstract

In this work an analysis of the intracluster light (ICL) in the galaxy cluster SMACS J0723.3-7327 (hereafter, SMACS J0723) using JWST/NIRCam deep imaging in six filters (F090W to F444W) is presented. The images were processed for low surface brightness (LSB) science, with additional correction for instrumental scattering in the short-wavelength channels, and analysed using wavelet-based decomposition. The ICL, brightest cluster galaxy (BCG), and satellite galaxies were extracted and modelled, with 2D maps for each component. ICL and ICL+BCG fractions, computed across all filters within a 400 kpc radius, exhibit a flat trend with wavelength, averaging 28% and 34%, respectively. Flux ratios between the BCG and the next brightest members (M${}_{12}$, M${}_{13}$ and M${}_{14}$) also display minimal wavelength dependence. These results indicate that SMACS J0723 is a dynamically evolved cluster with a dominant BCG and well-developed ICL. Five prominent ICL substructures are analysed, contributing to 10-12% of the total ICL+BCG flux budget, slightly exceeding simulation predictions. Their short dynamical timescales suggest an instantaneous ICL injection rate of several $10^3{L}_{\odot }{\mathrm{yr}}^{-1}$, consistent with active dynamical assembly. These findings support a scenario where SMACS J0723's ICL growth is currently driven by galaxy mergers involving the BCG and other bright satellites, rather than by the accretion of pre-processed ICL from a recent cluster merger. However, extrapolating the current injection rate to the cluster's lifetime indicates that additional mechanisms are required to match the growth observed in other clusters over cosmic times.

12 pages, 6 figures, accepted for publication in A&A

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Cited by in corpus (1)

• Euclid: Early Release Observations -- The Intracluster Light of Abell 2390