HerMES: A Deficit in the Surface Brightness of the Cosmic Infrared
  Background Due to Galaxy Cluster Gravitational Lensing
  We have observed four massive galaxy clusters with the SPIRE instrument on
the Herschel Space Observatory and measure a deficit of surface brightness
within their central region after subtracting sources. We simulate the effects
of instrumental sensitivity and resolution, the source population, and the
lensing effect of the clusters to estimate the shape and amplitude of the
deficit. The amplitude of the central deficit is a strong function of the
surface density and flux distribution of the background sources. We find that
for the current best fitting faint end number counts, and excellent lensing
models, the most likely amplitude of the central deficit is the full intensity
of the cosmic infrared background (CIB). Our measurement leads to a lower limit
to the integrated total intensity of the CIB of I(250 microns) >
0.69_(-0.03)^(+0.03) (stat.)_(-0.06)^(+0.11) (sys.) MJy/sr, with more CIB
possible from both low-redshift sources and from sources within the target
clusters. It should be possible to observe this effect in existing high angular
resolution data at other wavelengths where the CIB is bright, which would allow
tests of models of the faint source component of the CIB.
