Galaxy clusters enveloped by vast volumes of relativistic electrons.

The central regions of galaxy clusters are permeated by magnetic fields and filled with relativistic electrons. When clusters merge, the magnetic fields are amplified and relativistic electrons are re-accelerated by turbulence in the intracluster medium. These electrons reach energies of 1-10 GeV and, in the presence of magnetic fields, produce diffuse radio halos that typically cover an area of  around 1 Mpc.

Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event.

The Galactic Centre contains a supermassive black hole with a mass of four million Suns within an environment that differs markedly from that of the Galactic disk. Although the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings. Also, although the levels of star formation in the Galactic Centre have been approximately constant over the past few hundred million years, there is evidence of increased short-duration bursts, strongly influenced by the interaction of the black hole with the enhanced gas density present within the ring-like central molecular zone at Galactic longitude |l| < 0.

A large light-mass component of cosmic rays at 10(17)-10(17.5) electronvolts from radio observations.

Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 10(17)-10(18) electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies.

Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers.

We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes.