{\em Herschel}-ATLAS/GAMA: The Environmental Density of Far-Infrared
  Bright Galaxies at $z \leq 0.5$
  We compare the environmental and star formation properties of far-infrared
detected and non--far-infrared detected galaxies out to $z \sim0.5$. Using
optical spectroscopy and photometry from the Galaxy And Mass Assembly (GAMA)
and Sloan Digital Sky Survey (SDSS), with far-infrared observations from the
{\em Herschel}-ATLAS Science Demonstration Phase (SDP), we apply the technique
of Voronoi Tessellations to analyse the environmental densities of individual
galaxies. Applying statistical analyses to colour, $r-$band magnitude and
redshift-matched samples, we show there to be a significant difference at the
3.5$\sigma$ level between the normalized environmental densities of these two
populations. This is such that infrared emission (a tracer of star formation
activity) favours underdense regions compared to those inhabited by exclusively
optically observed galaxies selected to be of the same $r-$band magnitude,
colour and redshift. Thus more highly star-forming galaxies are found to reside
in the most underdense environments, confirming previous studies that have
proposed such a correlation. However, the degeneracy between redshift and
far-infrared luminosity in our flux-density limited sample means that we are
unable to make a stronger statement in this respect. We then apply our method
to synthetic light cones generated from semi-analytic models, finding that over
the whole redshift distribution the same correlations between star-formation
rate and environmental density are found.
