H-ATLAS/GAMA: The nature and characteristics of optically red galaxies
  detected at submillimetre wavelengths
  We combine Herschel/SPIRE sub-millimeter (submm) observations with existing
multi-wavelength data to investigate the characteristics of low redshift,
optically red galaxies detected in submm bands. We select a sample of galaxies
in the redshift range 0.01$\leq$z$\leq$0.2, having >5$\sigma$ detections in the
SPIRE 250 micron submm waveband. Sources are then divided into two sub-samples
of $red$ and $blue$ galaxies, based on their UV-optical colours. Galaxies in
the $red$ sample account for $\approx$4.2 per cent of the total number of
sources with stellar masses M$_{*}\gtrsim$10$^{10}$ Solar-mass. Following
visual classification of the $red$ galaxies, we find that $\gtrsim$30 per cent
of them are early-type galaxies and $\gtrsim$40 per cent are spirals. The
colour of the $red$-spiral galaxies could be the result of their highly
inclined orientation and/or a strong contribution of the old stellar
population.
  It is found that irrespective of their morphological types, $red$ and $blue$
sources occupy environments with more or less similar densities (i.e., the
$\Sigma_5$ parameter). From the analysis of the spectral energy distributions
(SEDs) of galaxies in our samples based on MAGPHYS, we find that galaxies in
the $red$ sample (of any morphological type) have dust masses similar to those
in the $blue$ sample (i.e. normal spiral/star-forming systems). However, in
comparison to the $red$-spirals and in particular $blue$ systems,
$red$-ellipticals have lower mean dust-to-stellar mass ratios. Besides galaxies
in the $red$-elliptical sample have much lower mean
star-formation/specific-star-formation rates in contrast to their counterparts
in the $blue$ sample. Our results support a scenario where dust in early-type
systems is likely to be of an external origin.
