25 MAGGIO 2021 ore 17:00

Early polarization science with POSSUM and ASKAP

Dr. Craig Anderson (NRAO, USA)
Early polarization science with POSSUM and ASKAP

The Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope is poised to survey the entire sky south of declination +40° in full polarisation to a sensitivity of ∼20μJy/beam, per Stokes parameter, at 10” spatial resolution. As part of this, the POSSUM (POlarisation Sky Survey of the Universe’s Magnetism) will generate a 3-pi-steradian Faraday rotation measure (RM) grid with a density of >30 RMs per square degree — a factor of >30 times higher than previous large area polarisation surveys, making it possible to routinely back-illuminate the magnetoionic structure of degree-scale foreground objects for the first time. Using POSSUM commissioning data, we have exploited these revolutionary capabilities to perform the first ever Faraday RM grid study of an individual low-mass cluster — the Fornax cluster — which is undergoing a complex series of mergers. The RM data uncover remarkable shocks, turbulence, and a massive new extended reservoir of warm baryons in the cluster, which are not currently detectable in other wavebands, nor by previous generations of radio telescope. I will discuss the implications for cluster astrophysics, the origin of cosmic magnetic fields, and the so-called ‘missing baryon problem’. I will finish by highlighting several new ASKAP polarisation studies in the works, which together showcase the extraordinary quality of ASKAP polarisation data, the groundbreaking science enabled by the dense POSSUM RM grid, and the exciting future for these techniques in the SKA era.


Breve CV del Dr. Craig Anderson:

Craig Anderson is a Jansky Fellow of the NRAO, U.S.A. (2019--present), and former Bolton Fellow of the CSIRO, Australia (2016--2019). His research focuses mainly on the physics of radio galaxies, including the internal composition and structure of radio lobes and jets, the modes of interaction between radio galaxies and their environments, and how these impact cosmic ecology and evolution. To achieve these ends, Craig has spent a large fraction of his time developing new observational techniques such as broadband radio spectropolarimetry, and on helping commission revolutionary new observational capabilities, such as broadband correlators and the ASKAP radio telescope.