Using strong lensing to understand the microJy radio emission in two
  radio quiet quasars at redshift 1.7
  The radio quasar luminosity function exhibits an upturn around
$L_{6\rm\:GHz}=10^{23}$ W Hz$^{-1}$ that is well-modelled by a star-forming
host galaxy population. This distribution leads some authors to cite star
formation as the main radio emission mechanism in so-called radio-quiet quasars
(RQQs). Understanding the origin of RQQ radio emission is crucial for our
understanding of quasar feedback mechanisms -- responsible for the regulation
of star-formation in the host galaxy -- and for understanding galaxy evolution
as a whole. By observing RQQs that have been magnified by strong gravitational
lensing, we have direct access to the RQQ population out to cosmic noon, where
evidence for twin mini-jets has recently been found in a sub-\textmu Jy RQQ.
Here we present radio observations of two lensed RQQs using the VLA at 5~GHz,
the latest objects to be observed in a sample of quadruply-imaged RQQs above
-30$^{\circ}$. In SDSS~J1004+4112 we find strong evidence for AGN-related radio
emission in the variability of the source. In PG~1115+080 we find tentative
evidence for AGN-related emission, determined by comparing the radio luminosity
with modelled dust components. If confirmed in the case of PG~1115+080, which
lies on the radio--FIR correlation, the result would reinforce the need for
caution when applying the correlation to rule out jet activity and when
assuming no AGN heating of FIR-emitting dust when calculating star formation
rates. Our programme so far has shown that two of the faintest radio sources
ever imaged show strong evidence for AGN-dominated radio emission.
