Last week's Colloquium: Observing galaxy clusters with LOFAR & LoTSS

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Clik here to view.© Andrea Botteon (Leiden University)

Mergers between galaxy clusters are the most energetic phenomena in the Universe. During these cosmic collisions, turbulence and shock waves are injected into the ICM and often generate cluster-wide synchrotron sources through a complex hierarchy of mechanisms that drain gravitational and electromagnetic energy into cosmic rays and magnetic fields.

These sources, termed radio halos and radio relics, are best studied at low-frequencies due to their steep spectra. LOFAR has recently opened a new observing window in the radio sky at low-frequency, allowing for a major step forward in the study of diffuse emission from the ICM.

In today's colloquium, I will report on very recent results based on LOFAR observations at 150 MHz of merging galaxy clusters. In particular, I will focus on the discovery of the most giant radio sources triggered by cluster mergers known to date. These detections demonstrate the existence of non-thermal components at great distances from cluster centers and on unprecedented large scales, with important implications on the models of magnetic field amplification and particle acceleration in the most dilute regions of the ICM.