Radio Loud and Radio Quiet Quasars
  We discuss 6 GHz JVLA observations covering a volume-limited sample of 178
low redshift ($0.2 < z < 0.3$) optically selected QSOs. Our 176 radio
detections fall into two clear categories: (1) About $20$\% are radio-loud QSOs
(RLQs) having spectral luminosities $L_6 \gtrsim 10^{\,23.2}
\mathrm{~W~Hz}^{-1}$ primarily generated in the active galactic nucleus (AGN)
responsible for the excess optical luminosity that defines a \emph{bona fide}
QSO. (2) The radio-quiet QSOs (RQQs) have $10^{\,21} \lesssim L_6 \lesssim
10^{\,23.2} \mathrm{~W~Hz}^{-1}$ and radio sizes $\lesssim 10 \mathrm{~kpc}$,
and we suggest that the bulk of their radio emission is powered by star
formation in their host galaxies. "Radio silent" QSOs ($L_6 \lesssim 10^{\,21}
\mathrm{~W~Hz}^{-1}$) are rare, so most RQQ host galaxies form stars faster
than the Milky Way; they are not "red and dead" ellipticals. Earlier radio
observations did not have the luminosity sensitivity $L_6 \lesssim 10^{\,21}
\mathrm{~W~Hz}^{-1}$ needed to distinguish between such RLQs and RQQs. Strong,
generally double-sided, radio emission spanning $\gg 10 \mathrm{~kpc}$ was
found associated with 13 of the 18 RLQ cores having peak flux densities
$S_\mathrm{p} > 5 \mathrm{~mJy~beam}^{-1}$ ($log(L) \gtrsim 24$). The radio
luminosity function of optically selected QSOs and the extended radio emission
associated with RLQs are both inconsistent with simple "unified" models that
invoke relativistic beaming from randomly oriented QSOs to explain the
difference between RLQs and RQQs. Some intrinsic property of the AGNs or their
host galaxies must also determine whether or not a QSO appears radio loud.
