Speaker
Description
LOFAR surveys have enabled unprecedentedly detailed analysis of large-scale, diffuse, and steep-spectrum sources in galaxy clusters, such as radio relics and halos. These are thought to arise from particle re-acceleration operated in the intra-cluster medium (ICM) by shocks and turbulence triggered by a cluster merger. Similar processes are likely also responsible for the re-ignition of fossil electrons from radio galaxies, thus forming amorphous and filamentary revived fossil sources . These are interesting targets to investigate the interplay between thermal and non-thermal components of the ICM, the injection of seed cosmic rays, the merging history of the host cluster, and the physics of radio filaments. Due to their ultra-steep synchrotron spectrum, a proper analysis of revived fossils requires sensitive and high-resolution multi-wavelength data at low radio frequencies. I will present the analysis of a sample of 7 candidate revived fossils, which have been selected by visual inspection of a sample of low-mass and nearby galaxy clusters in LoTSS-DR2 at 144 MHz, and then followed-up with the uGMRT at 400 MHz. I will show radio images, optical/X-ray overlays, and spatially-resolved spectral index maps that we used to interprete the nature of our targets. Our sample highlights challenges and opportunities in the selection and study of these sources in the SKA era.
| Topics | Galaxy Clusters & LSS (relativistic particles and magnetic fields) |
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