Speaker
Description
Gravitational waves from inflation may have left a detectable signature in the parity-odd, “B-mode” component of the polarization of the Cosmic Microwave Background (CMB). Detecting B-modes in the CMB would be “smoking gun” evidence for inflation and would probe some of the highest-energy physics in the known universe. However, current experiments have placed stringent upper limits on B-modes. If B-modes are present in the CMB, the signal is extremely faint and is dominated by polarized Galactic foregrounds at all frequencies. It is therefore essential to map polarized foregrounds with high precision to enable a detection of CMB B-modes. The Canadian Galactic Emission Mapper (CGEM) is a new 4m single-dish radio telescope at the Dominion Radio Astrophysical Observatory that is mapping polarized Galactic synchrotron emission from 8-10GHz over the Northern sky, with a planned counterpart in the Southern hemisphere. CGEM will greatly improve models of polarized CMB foregrounds and will hence be an important aid to current and future B-mode experiments. In this talk, I’ll give an overview of CGEM. I’ll then describe how we designed this purpose-built instrument to measure the sky with minimal polarization systematics, highlighting in particular the polarization purity of the optical design. I’ll also showcase early observations from a pathfinder version of CGEM, deployed in February 2025, which has been mapping the sky since. These data already show immense promise for future science with CGEM.