The WISE-2MASS Survey: Red Quasars Into the Radio Quiet Regime
  We present a highly complete sample of broad-line (Type 1) QSOs out to z ~ 3
selected by their mid-infrared colors, a method that is minimally affected by
dust reddening. We remove host galaxy emission from the spectra and fit for
excess reddening in the residual QSOs, resulting in a Gaussian distribution of
colors for unreddened (blue) QSOs, with a tail extending toward heavily
reddened (red) QSOs, defined as having E(B - V) > 0.25. This radio-independent
selection method enables us to compare red and blue QSO radio properties in
both the FIRST (1.4 GHz) and VLASS (2 - 4 GHz) surveys. Consistent with recent
results from optically-selected QSOs from SDSS, we find that red QSOs have a
significantly higher detection fraction and a higher fraction of compact radio
morphologies at both frequencies. We employ radio stacking to investigate the
median radio properties of the QSOs including those that are undetected in
FIRST and VLASS, finding that red QSOs have significantly brighter radio
emission and steeper radio spectral slopes compared with blue QSOs. Finally, we
find that the incidence of red QSOs is strongly luminosity dependent, where red
QSOs make up > 40% of all QSOs at the highest luminosities. Overall, red QSOs
comprise ~ 40% of higher luminosity QSOs, dropping to only a few percent at
lower luminosities. Furthermore, red QSOs make up a larger percentage of the
radio-detected QSO population. We argue that dusty AGN-driven winds are
responsible for both the obscuration as well as excess radio emission seen in
red QSOs.
