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Breakthrough Listen is a 10-yr initiative to search for signatures of technologies created by extraterrestrial civilisations at radio and optical wavelengths. Here, we detail the digital data recording system deployed for Breakthrough Listen observations at the 64-m aperture CSIRO Parkes Telescope in New South Wales, Australia. The recording system currently implements two modes: a dual-polarisation, 1.125-GHz bandwidth mode for single-beam observations, and a 26-input, 308-MHz bandwidth mode for the 21-cm multibeam receiver. The system is also designed to support a 3-GHz single-beam mode for the forthcoming Parkes ultra-wideband feed. In this paper, we present details of the system architecture, provide an overview of hardware and software, and present initial performance results.
We present the kpc-scale behaviour of the powerful extragalactic radio source Hercules A and the behaviour of the intracluster gas in which the radio source is situated. We have found that Hercules A exhibits a strong Laing-Garrington effect. The X-ray observations have revealed an extended X-ray emission elongated along the radio galaxy axis. The estimated temperature of the cluster is kT=2.45 keV and the central electron density is n○≃7.8×10−3 cm−3 which reveals a hot, dense environment in which Hercules A is situated. From the combined study of the radio and X-ray data we have estimated a central value of 3 ≲ B○(μG)≲9.
We also present the most recent results from the analysis of the radio data on the pc-scale structure of the radio galaxy, observed at 18 cm by the EVN–MERLIN array. A faint but compact radio source, coincident with the optical centre of Hercules A, was detected by the EVN at 18 mas resolution. The total flux density of the EVN core is 14.6 mJy. Its angular size is 18×7 mas with a position angle of ≃139°. There is also evidence for extended emission in the NW–SE direction, most probably from the eastern pc-scale jet. If this is true then there is a misalignment between the direction of the pc-eastern and the aligned kpc-scale jets of ≃35°.
Using radio and X-ray data of two powerful radio galaxies, we attempt to find out the role that radio jets (in terms of composition and power), as well as intracluster magnetic fields, play in the formation, propagation, and acceleration of cosmic rays. For this study we have selected the powerful radio galaxies Hercules A and 3C 310 because of the presence of ring-like features in their kpc-scale radio emission instead of the usual hotspots. These two FR1.5 lie at the center of galaxy cooling flow clusters in a dense environment. We observed the unique jets of Hercules both in kpc-scales (multifrequency VLA data) and pc-scales (EVN observations at 18 cm). We have also observed the core and inner jets of 3C310 at 18 cm using global VLBI. We report on the work in progress.
We search for extended regions of radio emission not associated with Active Galactic Nuclei, known as ‘relics’, ‘halos’ and ‘mini halos’, in a sample of 70 Abell clusters for which we have radio, optical and X-ray data. AGN can produce particle bubbles of non-thermal emission, which can restrict cosmic rays. Hence, radio relics and (mini) halos could be forming as a result of the confinement of cosmic rays by these bubbles. We are probing the role that intracluster magnetic fields (using Faraday rotation measure and inverse compton arguments), mergers (through radio/X-ray interactions), cooling flows (X-ray data), radio jets/shocks, as well as radio (mini) halos/relics, play in the formation, acceleration, and propagation of cosmic rays. For the current study, we have selected two powerful nearby radio galaxies from our sample: Hercules A and 3C 388. We report on the work in progress and future plans.
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