The polarization of the cosmic microwave background (CMB) provides a plethora of information about the early universe. Most notably, gravitational waves from the Inflationary epoch (the leading explanation of the origin of the universe) create a unique CMB polarization [Formula: see text]-mode signal. An unambiguous detection of the Inflationary [Formula: see text]-mode signal would be a window into the physics of the universe as it was [Formula: see text][Formula: see text]s after the Big Bang, at energy scales many orders of magnitude larger than what the LHC can produce. However, there are several instrumental and astrophysical sources that can obfuscate the Inflationary [Formula: see text]-mode signal. One of the most difficult parameters to calibrate for CMB telescopes is the absolute orientation of the antenna’s polarization sensitive axis. A miscalibration of the polarization orientation rotates the much brighter [Formula: see text]-mode signal, producing a false [Formula: see text]-mode signal. The current best uncertainty on polarization orientation in the CMB community is [Formula: see text], set from extrapolating IRAM measurements of the Crab Nebula supernova remnant at 90 GHz to 150 GHz, where the CMB signals peak. This accuracy is not sufficient to convincingly detect [Formula: see text]-modes predicted by currently allowable models of Inflation. We suggest to precisely measure the Crab Nebula’s polarization, which can be calibrated absolutely to [Formula: see text] from measurements of the polarized emission of Mars, and use these data to calibrate current and upcoming CMB experiments. In addition to Inflationary [Formula: see text]-modes, more precise calibration will allow us to better constrain the sum of the neutrino masses and set limits on exotic physics such as parity violation through cosmic polarization rotation.
The Crab Nebula as a Calibrator for Wide-beam Cosmic Microwave Background Polarization Surveys
