ATNF Marsfield Lecture Theatre

Dr Ettore Carretti

Deep polarization observations of the Galactic synchrotron emission in the southern sky. - Dr Ettore Carretti Colloquium

The Polarization of the Cosmic Microwave Background radiation (CMBP) allows us to investigate many processes of the primordial Universe. Inflation, scalar (density) and tensorial (gravitational waves) primordial perturbations, and formation processes of first stars and galaxies at the re-ionization age can be effectively studied through its angular power spectra. In spite of its importance, the CMBP signal is faint and its detection can be disturbed by astrophysical sources in the foreground. The Galactic synchrotron background emission is
expected to dominate the foreground contribution at frequencies lower than 100 GHz and can be properly studied at radio wavelengths, where its signal is stronger. The detection of this Galactic emission and study of its properties are thus crucial to understand the real CMBP possibilities to address its own scientific cases. Well studied on the Galactic plane, information about the synchrotron are scarse at high Galactic latitudes, which have the best CMBP observing conditions
because of the low Galactic contribution. After a short review of CMBP features, we report on the first observations of the polarized synchrotron emission carried out in low emission areas at high Galactic latitudes. Results and implications for CMBP studies will be discussed, especially those concerning the faint signature of the Inflation, which is expected to be of the order of 100 nK, or less. Finally, the Parkes Galactic Meridian Survey will be presented. Aimed at investigating the synchrotron behaviour along a Galactic meridian at 2.3 GHz, it is expected to reveal the unexplored synchrotron behaviour with respect to Galactic latitudes, significantly expanding our knowledge on the properties of this emission. It will also allow us to address Galactic physics topics, like the structure of the
magnetic field.