Multiwavelength radio observations of a Brightest Cluster Galaxy at
  z=1.71: Detection of a modest Active Galactic Nucleus and evidence for
  extended star formation
  We present deep, multiwavelength radio observations of
SpARCS104922.6+564032.5, a z = 1.71 galaxy cluster with a starbusting core.
Observations were made with the Karl G. Jansky Very Large Array (JVLA) in 3
bands: 1-2 GHz, 4-8 GHz and 8-12 GHz. We detect a radio source coincident with
the Brightest Cluster Galaxy (BCG) that has a spectral index of
{\alpha}=0.44\pm 0.29 and is indicative of emission from an Active Galactic
Nucleus. The radio luminosity is consistent with the average luminosity of the
lower redshift BCG sample, but the flux densities are 6{\sigma} below the
predicted values of the star-forming Spectral Energy Distribution based on far
infrared data. Our new fit fails to simultaneously describe the far infrared
and radio fluxes. This, coupled with the fact that no other bright source is
detected in the vicinity of the BCG implies that the star formation region,
traced by the infrared emission, is extended or clumpy and not located directly
within the BCG. Thus, we suggest that the star-forming core might not be driven
by a single major wet merger, but rather by several smaller galaxies stripped
of their gas or by a displaced cooling flow, although more data are needed to
confirm any of those scenarios.
