Fundamental differences in the radio properties of red and blue quasars:
  evolution strongly favoured over orientation
  A minority of the optically selected quasar population are red at optical
wavelengths due to the presence of dust along the line-of-sight. A key focus of
many red quasar studies is to understand their relationship with the overall
quasar population: are they blue quasars observed at a (slight) inclination
angle or do they represent a transitional phase in the evolution of quasars?
Identifying fundamental differences between red and blue quasars is key to
discriminate between these two paradigms. To robustly explore this, we have
uniformly selected quasars from the Sloan Digital Sky Survey with mid-infrared
counterparts, carefully controlling for luminosity and redshift effects. We
take a novel approach to distinguish between colour-selected quasars in the
redshift range of $0.2 < z < 2.4$ by constructing redshift-sensitive $g^* -
i^*$ colour cuts. From cross-matching this sample to the Faint Images of the
Radio Sky at Twenty-centimeters (FIRST) survey, we have found a factor
$\approx$ 3 larger fraction of radio-detected red quasars with respect to that
of blue quasars. Through a visual inspection of the FIRST images and an
assessment of the radio luminosities (rest-frame ${L_{\rm 1.4~GHz}}$ and
${L_{\rm 1.4~GHz}}/{L_{\rm 6\mu m}}$) we find that the radio-detection excess
for red quasars is primarily due to compact and radio-faint systems (around the
radio quiet--radio loud threshold). We show that our results rule out
orientation as the origin for the differences between red and blue quasars and
argue that they provide broad agreement with an evolutionary model.
