Isophotal signatures of the brightest cluster galaxy–intracluster light transition
Year: 2026
Type: article
Abstract: ABSTRACT The distinction between brightest cluster galaxies (BCGs) and intracluster light (ICL) remains ambiguous, with inferred cluster properties depending strongly on the adopted definition and measurement methodology. We report the presence of a common inflection feature in the radial profiles of surface brightness, ellipticity, and position angle of BCG + ICL systems, indicative of a structural transition in the underlying stellar distribution. Using a combination of low-redshift clusters ($z \lt 0.1$) observed with the Wendelstein Wide Field Imager, deep Hyper Suprime-Cam observations of clusters at $0.2 \lt z \lt 0.4$, and cosmological hydrodynamical simulations from Horizon-AGN and Hydrangea, we consistently identify a common inflection at radii of $60{-}85$ kpc. We interpret this feature as a characteristic transition in the combined BCG + ICL light distribution, that may reflect the hierarchical assembly of the cluster. The persistence of this feature across multiple photometric bands, redshift ranges, and simulations supports its robustness. To identify these transitions, we employ an automated second-derivative-based approach that does not rely on parametric decompositions or arbitrary surface brightness thresholds. This framework provides a physically motivated and scalable means to characterise the BCG–ICL transition, and it will be of paramount importance for forthcoming large-scale surveys such as the Legacy Survey of Space and Time and the European Space Agency’s Euclid mission.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
Funders: National Science Foundation, National Aeronautics and Space Administration, Princeton University, Johns Hopkins University, University of Maryland, University of Hawai'i, Ministry of Higher Education and Scientific Research, Space Telescope Science Institute, University of Edinburgh, Durham University, Japan Science and Technology Corporation, Ministry of Education, Culture, Sports, Science and Technology, Ministerio de Economía y Competitividad, National Astronomical Observatory of Japan, High Energy Accelerator Research Organization, Eötvös Loránd Tudományegyetem, Max-Planck-Institut für Astronomie, Toray Science Foundation, Smithsonian Astrophysical Observatory, Japan Society for the Promotion of Science, Japan Science and Technology Agency, Los Alamos National Laboratory
OpenAlex ID: W7221562423