Some merging galaxy clusters host diffuse extended radio emission , so-called radio halos and relics , unrelated to individual galaxies .
The origin of these halos and relics is still debated , although there is compelling evidence now that they are related to cluster merger events .
Here we present detailed Westerbork Synthesis Radio Telescope ( WSRT ) and Giant Metrewave Radio Telescope ( GMRT ) radio observations between 147 MHz and 4.9 GHz of a new radio-selected galaxy cluster 1RXS J0603.3+4214 , for which we find a redshift of 0.225 .
The cluster is detected as an extended X-ray source in the ROSAT All Sky Survey with an X-ray luminosity of L _ { { X,~ { } 0.1 - 2.4 ~ { } keV } } \sim 1 \times 10 ^ { 45 } erg s ^ { -1 } .
The cluster hosts a large bright 1.9 Mpc radio relic , an elongated \sim 2 Mpc radio halo , and two fainter smaller radio relics .
The large radio relic has a peculiar linear morphology .
For this relic we observe a clear spectral index gradient from the front of the relic towards the back , in the direction towards the cluster center .
Parts of this relic are highly polarized with a polarization fraction of up to 60 % .
We performed Rotation Measure ( RM ) Synthesis between 1.2 and 1.7 GHz .
The results suggest that for the west part of the large relic some of the Faraday rotation is caused by ICM and not only due to galactic foregrounds .
We also carried out a detailed spectral analysis of this radio relic and created radio color-color diagrams .
We find ( i ) an injection spectral index of -0.6 to -0.7 , ( ii ) steepening spectral index and increasing spectral curvature in the post-shock region , and ( iii ) an overall power-law spectrum between 74 MHz and 4.9 GHz with \alpha = -1.10 \pm 0.02 .
Mixing of emission in the beam from regions with different spectral ages is probably the dominant factor that determines the shape of the radio spectra .
Changes in the magnetic field , total electron content , or adiabatic gains/losses do not play a major role .
A model in which particles are ( re ) accelerated in a first order Fermi process at the front of the relic provides the best match to the observed spectra .
We speculate that in the post-shock region particles are re-accelerated by merger induced turbulence to form the radio halo as the relic and halo are connected .
The orientation of the bright relic and halo indicate a north-south merger event , but the peculiar linear shape and the presence of another relic , perpendicular to the bright relic , suggest a more complex merger event .
Deep X-ray observations will be needed to determine the merger scenario .