Herschel-ATLAS: blazars in the SDP field
  To investigate the poorly constrained sub-mm counts and spectral properties
of blazars we searched for these in the Herschel-ATLAS (H-ATLAS) science
demostration phase (SDP) survey catalog. We cross-matched 500$\mu$m sources
brighter than 50 mJy with the FIRST radio catalogue. We found two blazars, both
previously known. Our study is among the first blind blazar searches at sub-mm
wavelengths, i.e., in the spectral regime where little is still known about the
blazar SEDs, but where the synchrotron peak of the most luminous blazars is
expected to occur. Our early results are consistent with educated
extrapolations of lower frequency counts and question indications of
substantial spectral curvature downwards and of spectral upturns at mm
wavelengths. One of the two blazars is identified with a Fermi/LAT $\gamma$-ray
source and a WMAP source. The physical parameters of the two blazars are
briefly discussed.These observations demonstrate that the H-ATLAS survey will
provide key information about the physics of blazars and their contribution to
sub-mm counts.
