VLA and ALMA observations of the lensed radio-quiet quasar SDSS
  J0924+0219: a molecular structure in a 3 microJy radio source
  We present Karl G. Jansky Very Large Array (VLA) and Atacama Large Millimetre
Array (ALMA) observations of SDSS J0924+0219, a z = 1.524 radio-quiet lensed
quasar with an intrinsic radio flux density of about 3 micro-Jy. The four
lensed images are clearly detected in the radio continuum and the CO(5-4) line,
whose centroid is at z = 1.5254 +/- 0.0001, with a marginal detection in the
submillimetre continuum. The molecular gas displays ordered motion, in a
structure approximately 1--2.5 kpc in physical extent, with typical velocities
of 50-100 km/s. Our results are consistent with the radio emission being
emitted from the same region, but not with a point source of radio emission.
SDSS J0924+0219 shows an extreme anomaly in the flux ratios of the two merging
images in the optical continuum and broad emission lines, suggesting the
influence of microlensing by stars in the lensing galaxy. We find the flux
ratio in the radio, submillimetre continuum and CO lines to be slightly greater
than 1 but much less than that in the optical, which can be reproduced with a
smooth galaxy mass model and an extended source. Our results, supported by a
microlensing simulation, suggest that the most likely explanation for the
optical flux anomaly is indeed microlensing.
