The deepest Herschel-PACS far-infrared survey: number counts and
  infrared luminosity functions from combined PEP/GOODS-H observations
  We present results from the deepest Herschel-PACS (Photodetector Array Camera
and Spectrometer) far-infrared blank field extragalactic survey, obtained by
combining observations of the GOODS (Great Observatories Origins Deep Survey)
fields from the PACS Evolutionary Probe (PEP) and GOODS-Herschel key
programmes. We describe data reduction and the construction of images and
catalogues. In the deepest parts of the GOODS-S field, the catalogues reach
3-sigma depths of 0.9, 0.6 and 1.3 mJy at 70, 100 and 160 um, respectively, and
resolve ~75% of the cosmic infrared background at 100um and 160um into
individually detected sources. We use these data to estimate the PACS confusion
noise, to derive the PACS number counts down to unprecedented depths and to
determine the infrared luminosity function of galaxies down to LIR=10^11 Lsun
at z~1 and LIR=10^12 Lsun at z~2, respectively. For the infrared luminosity
function of galaxies, our deep Herschel far-infrared observations are
fundamental because they provide more accurate infrared luminosity estimates
than those previously obtained from mid-infrared observations. Maps and source
catalogues (>3-sigma) are now publicly released. Combined with the large wealth
of multi-wavelength data available for the GOODS fields, these data provide a
powerful new tool for studying galaxy evolution over a broad range of
redshifts.
