Abstract
ABSTRACT We estimate the intracluster light (ICL) component within a sample of 18 clusters detected in the XMM Cluster Survey (XCS) data using the deep (∼26.8 mag) Hyper Suprime-Cam Subaru Strategic Programme data release 1 i-band data. We apply a rest-frame μB = 25 mag arcsec−2 isophotal threshold to our clusters, below which we define light as the ICL within an aperture of RX,500 (X-ray estimate of R500) centred on the brightest cluster galaxy (BCG). After applying careful masking and corrections for flux losses from background subtraction, we recover ∼20 per cent of the ICL flux, approximately four times our estimate of the typical background at the same isophotal level (${\sim}5{{\ \rm per\ cent}}$). We find that the ICL makes up about ${\sim}24{{\ \rm per\ cent}}$ of the total cluster stellar mass on average (∼41 per cent 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-yr stacked imaging from the Vera C. Rubin Observatory).
Highlights
A complete understanding of the growth of universal large-scale structure (LSS) is one of the primary goals of modern cosmology
Henriques & Thomas (2010), building on the semi-analytic study of Brightest Cluster Galaxy (BCG) mass growth of De Lucia & Blaizot (2007), included a prescription for Intracluster Light (ICL); they found a mean fraction of ICL of around 18%, with a positive correlation between the ICL fraction and the halo mass of the cluster
We detect no strong trend between halo mass and the fraction of ICL; it is possible that any gradients present in Figure 13 are driven by the strong anti-correlation between the BCG flux fraction and halo mass established in Section 6, as they are not present with the ICL fraction itself
Summary
A complete understanding of the growth of universal large-scale structure (LSS) is one of the primary goals of modern cosmology. Structures which make up the ‘cosmic web’ include: ‘nodes’ (gravitationally-bound groups and clusters of galaxies), ‘filaments’ (lower-density connective ‘strings’ of galaxies) and ‘voids’ (vast under-densities of galaxies). For example, at individual cluster scales, there are numerous key inconsistencies (e.g. the baryonic matter fraction) This has motivated higher-resolution ‘zoom’ simulations with more complex ‘subgrid’ physics to better understand these differences (e.g. Barnes et al 017b), as well as applying semi-analytic models (SAMs) to simulated dark matter haloes There are tensions present between the observed stellar mass growth rate of BCGs (e.g. Collins et al 2009; Burke et al 2012) and that in simulations
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