Deep Very Large Array observations of the merging cluster CIZA
  J2242.8+5301: continuum and spectral imaging
  Despite progress in understanding radio relics, there are still open
questions regarding the underlying particle acceleration mechanisms. In this
paper we present deep 1--4 GHz VLA observations of CIZA\,J2242.8+5301
($z=0.1921$), a double radio relic cluster characterized by small projection on
the plane of the sky. Our VLA observations reveal, for the first time, the
complex morphology of the diffuse sources and the filamentary structure of the
northern relic. We discover new faint diffuse radio emission extending north of
the main northern relic. Our Mach number estimates for the northern and
southern relics, based on the radio spectral index map obtained using the VLA
observations and existing LOFAR and GMRT data, are consistent with previous
radio and X-ray studies ($\mathcal{M}_{\rm RN}=2.58\pm0.17$ and
$\mathcal{M}_{\rm RS}=2.10\pm0.08$). However, color-color diagrams and
modelings suggest a flatter injection spectral index than the one obtained from
the spectral index map, indicating that projection effects might be not
entirely negligible. The southern relic consists of five "arms". Embedded in
it, we find a tailed radio galaxy which seems to be connected to the relic. A
spectral index flattening, where the radio tail connects to the relic, is also
measured. We propose that the southern relic may trace AGN fossil electrons
that are re-accelerated at a shock, with an estimated strength of
$\mathcal{M}=2.4$. High-resolution mapping of other tailed radio galaxies also
supports a scenario where AGN fossil electrons are revived by the merger event
and could be related to the formation of some diffuse cluster radio emission.
