Galaxy And Mass Assembly (GAMA): Defining Passive Galaxy Samples and
  Searching for the UV Upturn
  We use data from the GAMA and GALEX surveys to demonstrate that the UV
upturn, an unexpected excess of ultraviolet flux from a hot stellar component,
seen in the spectra of many early-type galaxies, arises from processes internal
to individual galaxies with no measurable influence from the galaxies' larger
environment. We first define a clean sample of passive galaxies without a
significant contribution to their UV flux from low-level star formation. We
confirm that galaxies with the optical colours of red sequence galaxies often
have signs of residual star formation, which, without other information, would
prevent a convincing demonstration of the presence of UV upturns. However, by
including (NUV$-u$) and {\it WISE} (W2-W3) colours, and FUV data where it
exists, we can convincingly constrain samples to be composed of
non-star-forming objects. Using such a sample, we examine GALEX photometry of
low redshift GAMA galaxies in a range of low-density environments, from groups
to the general field, searching for UV upturns. We find a wide range of
(NUV$-r$) colours, entirely consistent with the range seen -- and attributed to
the UV upturn -- in low-redshift red sequence cluster galaxies. The range of
colours is independent of group multiplicity or velocity dispersion, with
isolated passive galaxies just as likely to have blue UV-to-optical colours,
implying significant upturn components, as those in richer groups and in the
previous data on clusters. This is supported by equivalent results for
(FUV$-r$) colours which are clear indicators of upturn components.
