Speaker
Description
Synchrotron diffuse emission at the centre of merging galaxy clusters and along filaments connecting them demonstrates the presence of relativistic particles and magnetic fields in these environments. Their properties represent a unique tool to constrain large-scale magnetic fields and the physics of the acceleration and transport of the relativistic particles. However, radio observations of these sources in total intensity are heavily limited by confusion of background radio sources (confusion noise). Polarization observations are less affected by confusion noise, due to the lower density of polarized sources with respect to total intensity. Nevertheless, despite technological progress, the detection of the polarization signal is still challenging due to its weakness. Recently, for the first time, we detected at the centre of a galaxy cluster a large-scale diffuse polarized emission extending up to scales of about 2.5 Mpc, i.e. up to the periphery of the cluster, where the total intensity is not detected likely due to observational limitations. This detection is particularly important because the polarized emission of these sources allows us to put constraints on the strength and the structure of the magnetic field relatively independently on the relativistic electron population.
In order to assess the capabilities of the SKA telescopes to observe these sources, we use cosmological magneto-hydrodynamical simulations to predict the expected full Stokes surface brightness of diffuse synchrotron sources at the centre of galaxy clusters and in filaments connecting them in the frequency band 950–1760 MHz. We explore the possibility to detect these sources with short observations (~15 minutes, as for the SKA-MID polarization survey planned by the SKA Magnetism Science Working Group) and with longer pointed observations. These simulations show that pointed observations are required in order to reveal these sources. Thanks to the unprecedented combination of sensitivity and spatial resolution, these observations will permit us to constraint the magnetic field properties and to understand if the energy density of relativistic electrons is in equipartition with the magnetic field or rather coupled with the thermal gas density. This will add a precious piece of information to our understanding of cosmological magnetic fields history.
| Topics | Galaxy Clusters & LSS (relativistic particles and magnetic fields) |
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