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We present deep LOFAR observations between 120-181 MHz of the Toothbrush (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of $alpha = -0.8 pm 0.1$ at the northern edge of the main radio relic, steepening towards the south to $alpha approx - 2$. The spectral index of the radio halo is remarkably uniform ($alpha = -1.16$, with an intrinsic scatter of $leq 0.04$). The observed radio relic spectral index gives a Mach number of $mathcal{M} = 2.8^{+0.5}_{-0.3}$, assuming diffusive shock acceleration (DSA). However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock ($mathcal{M} approx 1.2$, with an upper limit of $mathcal{M} approx 1.5$). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks.
We present the results of Suzaku observations of the galaxy cluster 1RXS J0603.3+4214 with toothbrush radio relic. Although a shock with Mach number $M simeq 4$ is expected at the outer edge of the relic from the radio observation, our temperature me
Radio halos are extended ($sim{rm Mpc}$), steep-spectrum sources found in the central region of dynamically disturbed clusters of galaxies. Only a handful of radio halos have been reported to reside in galaxy clusters with a mass $M_{500}lesssim5time
Previous studies have shown that CIZA J2242.8+5301 (the Sausage cluster, $z=0.192$) is a massive merging galaxy cluster that hosts a radio halo and multiple relics. In this paper we present deep, high fidelity, low-frequency images made with the LOw-
We present LOFAR $120-168$ MHz images of the merging galaxy cluster Abell 1240 that hosts double radio relics. In combination with the GMRT $595-629$ MHz and VLA $2-4$ GHz data, we characterised the spectral and polarimetric properties of the radio e
We present the results of deep 140 ks Suzaku X-ray observations of the north-east (NE) radio relic of the merging galaxy cluster Abell2255. The temperature structure of Abell2255 is measured out to 0.9 times the virial radius (1.9 Mpc) in the NE dire