Microwave Spectro-Polarimetry of Matter and Radiation across Space and\n Time

This paper discusses the science case for a sensitive spectro-polarimetric\nsurvey of the microwave sky. Such a survey would provide a tomographic and\ndynamic census of the three-dimensional distribution of hot gas, velocity\nflows, early metals, dust, and mass distribution in the entire Hubble volume,\nexploit CMB temperature and polarisation anisotropies down to fundamental\nlimits, and track energy injection and absorption into the radiation background\nacross cosmic times by measuring spectral distortions of the CMB blackbody\nemission. In addition to its exceptional capability for cosmology and\nfundamental physics, such a survey would provide an unprecedented view of\nmicrowave emissions at sub-arcminute to few-arcminute angular resolution in\nhundreds of frequency channels, a data set that would be of immense legacy\nvalue for many branches of astrophysics. We propose that this survey be\ncarried-out with a large space mission featuring a broad-band polarised imager\nand a moderate resolution spectro-imager at the focus of a 3.5m aperture\ntelescope actively cooled to about 8K, complemented with absolutely-calibrated\nFourier Transform Spectrometer modules observing at degree-scale angular\nresolution in the 10-2000 GHz frequency range. We propose two observing modes:\na survey mode to map the entire sky as well as a few selected wide fields, and\nan observatory mode for deeper observations of regions of specific interest.\n