Speaker
Description
In this talk, I will present the first LOFAR LBA observations of the well-known galaxy cluster CIZA J2242.8+5301 (the “Sausage” cluster), reaching a thermal-noise limited sensitivity of 1.5 mJy/beam at 15″ resolution. This system is not only a benchmark for studying radio relics, but also one of the very few galaxy clusters observed with LOFAR LBA to date. The 45 MHz observations represent the lowest-frequency imaging of this cluster to date, unveiling a complex network of diffuse emission beyond the prominent double radio relics. Focusing on the northern relic, I will show that its surface brightness profile appears remarkably symmetric, in contrast to expected standard sharp-shock plus radiative cooling scenario. To interpret this, we used an analytic model to reproduce the profile incorporating projection effects, magnetic field variations, and shock surface irregularities. These results suggest that additional mechanisms may be at play in producing relic emission, challenging shocks formation models in cluster outskirts. This work also demonstrates the capabilities of LOFAR LBA and its related calibration pipeline for detailed studies of diffuse radio emission, and in particular radio relics, at very-low radio frequencies.
