UV upturn versus UV weak galaxies: differences and similarities of their
  stellar populations unveiled by a de-biased sample
  The ultraviolet (UV) upturn is characterised by an unexpected up-rise of the
UV flux in quiescent galaxies between the Lyman limit and 2500\AA. By making
use of colour-colour diagrams, one can subdivide UV bright red-sequence
galaxies in two groups: UV weak and upturn. With these two groups, we propose a
comparison between their stellar population properties with the goal of
establishing differences and similarities between them. We make use of
propensity score matching (PSM) to mitigate potential biases between the two
samples, by selecting similar objects in terms of redshift and stellar mass.
Also, we take advantage of spectral energy distribution (SED) fitting results
from magphys made available by the GAMA collaboration. The analyses are made by
comparing the distributions from the SED fitting directly, as well as
investigating the differences in correlations between their parameters, and
finally by using principal component analysis (PCA). We explore important
differences and similarities between UV weak and upturn galaxies in terms of
several parameters, such as: metallicity, age, specific star formation rate,
time of last burst of star-formation, to mention a few. Notable differences are
those concerning (g-r) colour, metallicity, and time since last burst of
star-formation: UV upturn are redder in the optical, more metallic, and their
last burst of star-formation happened earlier in time. These differences
suggest that UV upturn systems have shorter star-formation histories (i.e. have
been evolving more passively) when compared to UV weak galaxies. Consequently,
these last seem to have a higher diversity of stellar populations.
