THE RADIO RELICS AND HALO OF EL GORDO, A MASSIVE z = 0.870 CLUSTER MERGER

We present 610 MHz and 2.1 GHz imaging of the massive Sunyaev-Zel'dovich Effect selected z = 0.870 cluster merger ACT-CL J0102-4915 ("El Gordo"), obtained with the Giant Metrewave Radio Telescope and the Australia Telescope Compact Array (ATCA), respectively. We detect two complexes of radio relics separated by 3.' 4 (1.6Mpc) along the system's northwest-to-southeast collision axis that have high integrated polarization fractions (33%) and steep spectral indices (alpha between 1 and 2; S-nu proportional to nu(-alpha)), consistent with creation via Fermi acceleration by shocks in the intracluster medium triggered by the cluster collision. From the spectral index of the relics, we compute a Mach number M = 2.5(-0.3)(+0.7) and shock speed of 2500(-300)(+400) km s(-1). With our wide-bandwidth, full-polarization ATCA data, we compute the Faraday depth phi across the northwest relic and find a range of values spanning Delta phi = 30 rad m(-2), with a mean value of = 11 rad m-2 and standard deviation sigma(phi) = 6 rad m(-2). With the integrated line-of-sight gas density derived from new Chandra X-ray observations, our Faraday depth measurement implies B-parallel to similar to 0.01 mu G in the cluster outskirts. The extremely narrow shock widths in the relics (d(shock) <= 23 kpc), caused by the short synchrotron cooling timescale of relativistic electrons at z = 0.870, prevent us from placing a meaningful constraint on the magnetic field strength B using cooling time arguments. In addition to the relics, we detect a large (r(H) similar or equal to 1.1Mpc radius), powerful (log(L-1.4/WHz(-1)) = 25.66 +/- 0.12) radio halo with a shape similar to El Gordo's "bullet"-like X-ray morphology. The spatially resolved spectral-index map of the halo shows the synchrotron spectrum is flattest near the relics, along the system's collision axis, and in regions of high T-gas, all locations associated with recent energy injection. The spatial and spectral correlation between the halo emission and cluster X-ray properties supports primary-electron processes like turbulent reacceleration as the halo production mechanism. The halo's integrated 610MHz to 2.1 GHz spectral index is a relatively flat alpha = 1.2 +/- 0.1, consistent with the cluster's high Tgas in view of previously established global scaling relations. El Gordo is the highest-redshift cluster known to host a radio halo and/or radio relics, and provides new constraints on the non-thermal physics in clusters at z > 0.6.