Disentangling the ICL with the CHEFs: Abell 2744 as a case study

TL;DR

This paper introduces a novel CHEFs-based algorithm to measure intracluster light (ICL) fractions in galaxy clusters without prior assumptions, successfully applied to Abell 2744, yielding results consistent with simulations.

Contribution

The authors developed a new CHEFs-based method to disentangle ICL from galaxy light without assumptions on ICL properties, improving accuracy and objectivity.

Findings

ICL fraction in Abell 2744 is approximately 19.17%.

The method effectively separates ICL from galaxy luminosity.

Results align with numerical simulation predictions.

Abstract

Measurements of the intracluster light (ICL) are still prone to methodological ambiguities and there are multiple techniques in the literature for that purpose, mostly based on the binding energy, the local density distribution, or the surface brightness. A common issue with these methods is the a priori assumption of a number of hypotheses on either the ICL morphology, its surface brightness level or some properties of the brightest cluster galaxy (BCG). The discrepancy on the results is high, and numerical simulations just bound the ICL fraction in present-day galaxy clusters to the range 10-50%. We developed a new algorithm based on the Chebyshev-Fourier functions (CHEFs) to estimate the ICL fraction without relying on any a priori assumption on the physical or geometrical characteristics of the ICL. We are able to not only disentangle the ICL from the galatic luminosity but mark out the limits of the BCG from the ICL in a natural way. We test our tecnique with the recently released data of the cluster Abell 2744, observed by the Frontier Fields program. The complexity of this multiple merging cluster system and the formidable depth of these images make it a challenging test case to prove the efficiency of our algorithm. We found a final ICL fraction of 19.17+-2.87%, which is very consistent with numerical simulations.