Growth of Intracluster Light in XCS-HSC Galaxy Clusters

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Kate E. Furnell (1), Chris A. Collins (1), Lee S. Kelvin (1,2), Ivan K. Baldry (1), Phil A. James (1), Maria Manolopoulou (3), Robert G. Mann (3), Paul A. Giles (4), Alberto Bermeo (4), Matthew Hilton (5,6), Reese Wilkinson (4), A. Kathy Romer (4), Carlos Vergara (4), Sunayana Bhargava (4), John P. Stott (7), Julian Mayers (4), Pedro Viana (8,9) ((1) Astrophysics Research Institute, Liverpool John Moores University, (2) Department of Astrophysical Sciences, Princeton University, (3) Institute for Astronomy, University of Edinburgh, (4) Department of Physics and Astronomy, University of Sussex, (5) Astrophysics Research Centre, University of KwaZulu-Natal, (6) School of Mathematics, Statistics \& Computer Science, University of KwaZulu-Natal, (7) Department of Physics, Lancaster University, (8) Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, (9) Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto)

We estimate the Intracluster Light (ICL) component within a sample of 18 clusters detected in XMM Cluster Survey (XCS) data using deep (∼ 26.8 mag) Hyper Suprime Cam Subaru Strategic Program DR1 (HSC-SSP DR1) i-band data. We apply a rest-frame μB=25 mag/arcsec2 isophotal threshold to our clusters, below which we define light as the ICL within an aperture of RX,500 (X-ray estimate of R500) centered on the Brightest Cluster Galaxy (BCG). After applying careful masking and corrections for flux losses from background subtraction, we recover ∼20% of the ICL flux, approximately four times our estimate of the typical background at the same isophotal level (∼ 5%). We find that the ICL makes up about ∼ 24% of the total cluster stellar mass on average (∼ 41% including the flux contained in the BCG within 50 kpc); this value is well-matched with other observational studies and semi-analytic/numerical simulations, but is significantly smaller than results from recent hydrodynamical simulations (even when measured in an observationally consistent way). We find no evidence for any links between the amount of ICL flux with cluster mass, but find a growth rate of 2−4 for the ICL between 0.1<z<0.5. We conclude that the ICL is the dominant evolutionary component of stellar mass in clusters from z∼1. Our work highlights the need for a consistent approach when measuring ICL alongside the need for deeper imaging, in order to unambiguously measure the ICL across as broad a redshift range as possible (e.g. 10-year stacked imaging from the Vera C. Rubin Observatory).

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