HerMES: A search for high-redshift dusty galaxies in the HerMES Large
  Mode Survey - Catalogue, number counts and early results
  Selecting sources with rising flux densities towards longer wavelengths from
Herschel/SPIRE maps is an efficient way to produce a catalogue rich in
high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this
approach has already been confirmed by spectroscopic follow-up observations,
but the previously available catalogues made this way are limited by small
survey areas. Here we apply a map-based search method to 274 deg$^2$ of the
HerMES Large Mode Survey (HeLMS) and create a catalogue of 477 objects with
SPIRE flux densities $S_{500} > S_{350} >S_{250}$ and a $5 \sigma$ cut-off
$S_{500} > $ 52 mJy. From this catalogue we determine that the total number of
these "red" sources is at least an order of magnitude higher than predicted by
galaxy evolution models. These results are in agreement with previous findings
in smaller HerMES fields; however, due to our significantly larger sample size
we are also able to investigate the shape of the red source counts for the
first time. We have obtained spectroscopic redshift measurements for two of our
sources using the Atacama Large Millimeter/submillimeter Array (ALMA). The
redshifts z = 5.1 and z = 3.8 confirm that with our selection method we can
indeed find high-redshift dusty star-forming galaxies.
