Year: 2026
Type: article
Abstract: We present a model-based framework to define an aperture separation between the brightest cluster galaxy (BCG) and the intracluster light (ICL). Using the intrinsic BCG and ICL components predicted by the semianalytic model FEGA25 , we determine, for each halo, the aperture radius that minimizes the bias in the recovered ICL mass. The optimal radius is obtained by balancing the BCG stellar mass lying outside the aperture with the ICL mass enclosed within it. At z = 0, the optimal aperture in physical units increases with halo mass approximately as r cut ∝ M halo 0.28 , close to the expected virial scaling. When expressed in units of the virial radius, the aperture becomes nearly independent of halo mass, with r cut / R vir ≃ 0.045 at 10 14 M ⊙ . Applying the resulting aperture prescriptions, we recover the intrinsic BCG mass to better than 8% (lowest percentile), while the ICL mass is recovered with median values very close to unity and an average scatter of ±3%. Extending the analysis to z = 1 and 2, we find that the mass trends remain similar, with both the slope and intercept of the r cut / R vir relation remaining stable. Robustness tests show that the inferred aperture is most sensitive to the ICL concentration and BCG size, but the main trends are preserved. Our results provide a physically motivated aperture definition for connecting observational BCG–ICL measurements to intrinsic model components.
Authors: Emanuele Contini, Sukyoung K. Yi
Institution: Yonsei University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funder: National Research Foundation
OpenAlex ID: W7169876405