Fundamental differences in the radio properties of red and blue quasars:
  enhanced compact AGN emission in red quasars
  We have recently used the Faint Images of the Radio Sky at Twenty-centimeters
(FIRST) survey to show that red quasars have fundamentally different radio
properties to typical blue quasars: a significant (factor $\sim3$) enhancement
in the radio-detection fraction, which arises from systems around the
radio-quiet threshold with compact ($<5''$) radio morphologies. To gain greater
insight into these physical differences, here we use the DR14 Sloan Digital Sky
Survey (SDSS) and more sensitive, higher resolution radio data from the Very
Large Array (VLA) Stripe 82 (S82) and VLA-COSMOS 3 GHz (C3GHz) surveys. With
the S82 data, we perform morphological analyses at a resolution and depth three
times that of the FIRST radio survey, and confirm an enhancement in radio-faint
and compact red quasars over typical quasars; we now also find tentative
evidence for an enhancement in red quasars with slightly extended radio
structures ($16-43$ kpc at $z=1.5$). These analyses are complemented by C3GHz,
which is deep enough to detect radio emission from star-formation processes.
From our data we find that the radio enhancement from red quasars is due to AGN
activity on compact scales ($< 43$ kpc) for radio-intermediate-radio-quiet
sources ($-5<R<-3.4$, where $R=L_{1.4GHz}/L_{6 \mu m}$), which decreases at
$R<-5$ as the radio emission from star-formation starts to dilute the AGN
component. Overall our results argue against a simple orientation scenario and
are consistent with red quasars representing a younger, earlier phase in the
overall evolution of quasars.
