Coffee talks
Friday 29/05/2020 @ 11:30, On-line
Chiara Stuardi (University of Bologna / IRA-INAF), "Magnetic fields beyond galaxy clusters: a LOFAR polarization study of giant radio galaxies"
Lobes of giant radio galaxies (GRGs, i.e. larger than 0.7 Mpc) are usually found outside of dense regions and interact with the Warm-Hot Intergalactic Medium (WHIM). Their polarization properties can be used to study the magneto-ionic properties of the WHIM. Because of Faraday depolarization, low-frequency polarization observations are particularly useful to probe the most rarefied region of the Universe since they select only the sources which lie in low-density and weak-magnetic field environments. We present a polarization study of a large sample of 239 GRGs performed at 144 MHz with LOFAR. The polarization detection rate varies with the GRG's size and projected distance from galaxy clusters. The observed level of depolarization allowed us to derive an upper limit of 0.1\muG to the magnetic field of the WHIM, with fluctuations on kpc scales and thermal electron densities below 10^-5 cm^-3. This work shows that these sources can give us insights into an under-explored part of our Universe.