RX J0603.3+4214 LOFAR 58GHz images

The resulting image was combined with observations at higher frequencies (LOFAR 150MHz and VLA 1500MHz) to extract spectral information.Results.We obtained the first thermal-noise limited image from an observation carried out with the LOFAR LBA system using allDutch stations at a central frequency of 58MHz. With eight hours of data, we reached an rms noise of 1.3mJy/beam at a resolution of 18"x11". The procedure we developed is an important step towards routine high-fidelity imaging with the LOFAR LBA.

Theanalysis of the radio spectra shows that the radio relic extends to distances of 800kpc downstream from the shock front, larger than what is allowed by electron cooling time. Furthermore, the shock wave started accelerating electrons already at a projected distance of <300kpc from the crossing point of the two clusters. These results may be explained by electrons being re-accelerated down stream by background turbulence, possibly combined with projection effects with respect to the radio halo.