Observations of the galaxy cluster CIZA J2242.8+5301 with the Sardinia
  Radio Telescope
  We observed the galaxy cluster CIZA J2242.8+5301 with the Sardinia Radio
Telescope to provide new constraints on its spectral properties at high
frequency. We conducted observations in three frequency bands centred at 1.4
GHz, 6.6 GHz and 19 GHz, resulting in beam resolutions of 14$^{\prime}$,
2.9$^{\prime}$ and 1$^{\prime}$ respectively. These single-dish data were also
combined with archival interferometric observations at 1.4 and 1.7 GHz. From
the combined images, we measured a flux density of ${\rm
S_{1.4GHz}=(158.3\pm9.6)\,mJy}$ for the central radio halo and ${\rm
S_{1.4GHz}=(126\pm8)\,mJy}$ and ${\rm S_{1.4GHz}=(11.7\pm0.7)\,mJy}$ for the
northern and the southern relic respectively. After the spectral modelling of
the discrete sources, we measured at 6.6 GHz ${\rm
S_{6.6GHz}=(17.1\pm1.2)\,mJy}$ and ${\rm S_{6.6GHz}=(0.6\pm0.3)\,mJy}$ for the
northern and southern relic respectively. Assuming simple diffusive shock
acceleration, we interpret measurements of the northern relic with a continuous
injection model represented by a broken power-law. This yields an injection
spectral index ${\rm \alpha_{inj}=0.7\pm0.1}$ and a Mach number ${\rm
M=3.3\pm0.9}$, consistent with recent X-ray estimates. Unlike other studies of
the same object, no significant steepening of the relic radio emission is seen
in data up to 8.35 GHz. By fitting the southern relic spectrum with a simple
power-law (${\rm S_{\nu}\propto\nu^{-\alpha}}$) we obtained a spectral index
${\rm \alpha\approx1.9}$ corresponding to a Mach number (${\rm M\approx1.8}$)
in agreement with X-ray estimates. Finally, we evaluated the rotation measure
of the northern relic at 6.6 GHz. These results provide new insights on the
magnetic structure of the relic, but further observations are needed to clarify
the nature of the observed Faraday rotation.
