HerMES: deep number counts at 250, 350, and 500 microns in the COSMOS
  and GOODS-N fields and the build-up of the cosmic infrared background
  ABRIGED Herschel/SPIRE has provided confusion limited maps of deep fields at
250, 350, and 500um, as part of the HerMES survey. Due to confusion, only a
small fraction of the Cosmic Infrared Background can be resolved into
individually-detected sources. Our goal is to produce deep galaxy number counts
and redshift distributions below the confusion limit, which we then use to
place strong constraints on the origins of the cosmic infrared background and
on models of galaxy evolution.
  We individually extracted the bright SPIRE with a method using the positions,
the flux densities, and the redshifts of the 24um sources as a prior, and
derived the number counts and redshift distributions of the bright SPIRE
sources. For fainter SPIRE sources, we reconstructed the number counts and the
redshift distribution below the confusion limit using the deep 24um catalogs
associated with photometric redshift and information provided by the stacking
of these sources into the deep SPIRE maps. Finally, by integrating all these
counts, we studied the contribution of the galaxies to the CIB as a function of
their flux density and redshift.
  Through stacking, we managed to reconstruct the source counts per redshift
slice down to ~2 mJy in the three SPIRE bands, which lies about a factor 10
below the 5sigma confusion limit. None of the pre-existing population models
are able to reproduce our results at better than 3sigma. Finally, we
extrapolate our counts to zero flux density in order to derive an estimate of
the total contribution of galaxies to the CIB, finding 10.1, 6.5, and 2.8
nW/m2/sr at 250, 350, and 500um, respectively. These values agree well with
FIRAS absolute measurements, suggesting our number counts and their
extrapolation are sufficient to explain the CIB. Finally, combining our results
with other works, we estimate the energy budget contained in the CIB between 8
and 1000um: 26 nW/m2/sr.
