The Growth of Intracluster Light in XCS-HSC Galaxy Clusters from $0.1 <
  z < 0.5$
  We estimate the Intracluster Light (ICL) component within a sample of 18
clusters detected in XMM Cluster Survey (XCS) data using deep ($\sim$ 26.8 mag)
Hyper Suprime Cam Subaru Strategic Program DR1 (HSC-SSP DR1) $i$-band data. We
apply a rest-frame ${\mu}_{B} = 25 \ \mathrm{mag/arcsec^{2}}$ isophotal
threshold to our clusters, below which we define light as the ICL within an
aperture of $R_{X,500}$ (X-ray estimate of $R_{500}$) centered on the Brightest
Cluster Galaxy (BCG). After applying careful masking and corrections for flux
losses from background subtraction, we recover $\sim$20% of the ICL flux,
approximately four times our estimate of the typical background at the same
isophotal level ($\sim$ 5%). We find that the ICL makes up about $\sim$ 24% of
the total cluster stellar mass on average ($\sim$ 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 $z \sim
1$. 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).
