The discovery of lensed radio and X-ray sources behind the Frontier
  Fields cluster MACS J0717.5+3745 with the JVLA and Chandra
  We report on high-resolution JVLA and Chandra observations of the HST
Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest
contiguous magnified area of any known cluster, making it a promising target to
search for lensed radio and X-ray sources. With the high-resolution 1.0-6.5 GHz
JVLA imaging in A and B configuration, we detect a total of 51 compact radio
sources within the area covered by the HST imaging. Within this sample we find
7 lensed sources with amplification factors larger than $2$. None of these
sources are identified as multiply-lensed. Based on the radio luminosities, the
majority of these sources are likely star forming galaxies with star formation
rates of 10-50 M$_\odot$ yr$^{-1}$ located at $1 \lesssim z \lesssim 2$. Two of
the lensed radio sources are also detected in the Chandra image of the cluster.
These two sources are likely AGN, given their $2-10$ keV X-ray luminosities of
$\sim 10^{43-44}$ erg s$^{-1}$. From the derived radio luminosity function, we
find evidence for an increase in the number density of radio sources at
$0.6<z<2.0$, compared to a $z < 0.3$ sample. Our observations indicate that
deep radio imaging of lensing clusters can be used to study star forming
galaxies, with star formation rates as low as $\sim10$ M$_{\odot}$ yr$^{-1}$,
at the peak of cosmic star formation history.
