CosmoglobeHD: Mapping the universe from the Milky Way to the Big Bang in high resolution

The Cosmic Microwave Background (CMB) is the first light emitted in the Universe. By studying it, we can understand how the first elements were formed, how the first stars and galaxies evolved, and even how the Universe began. The exact color of the CMB not only tells us the temperature of the Universe, but it also traces every energetic event in history, such as the first supernovae, the evolution of intergalactic plasma, and potentially the annihilation of dark matter into gamma rays. At the same time, the tiny changes in temperature and polarization of the CMB across the sky can tell us the relative amount of normal matter and dark matter. Polarization measurements directly probe the existence of gravitational waves, and would provide direct evidence for the source of the initial expansion of the universe, cosmic inflation. CosmoglobeHD will use the most sensitive data available to measure the color of the Big Bang and constrain primordial gravitational waves. To achieve this, we will create highly sensitive maps of the intervening material between us and the CMB, including dust from the Solar System and the Milky Way. The primary datasets will be from the Nobel Prize-winning COBE/FIRAS satellite experiment and the upcoming Simons Observatory data. The FIRAS experiment constrained the CMB to be the most perfectly thermal source found in nature. Standard cosmological models predict non-thermal emission just below the reported FIRAS errors. This project will improve these constraints through modern algorithmic techniques, while using our improved knowledge of the Milky Way obtained through NASA's WMAP and ESA's Planck satellites. Meanwhile, the Simons Observatory's search for inflation is limited both by detector sensitivity and modeling of the Milky Way. By combining the sensitive Simons Observatory maps with independent satellite-based data including FIRAS, WMAP, and Planck, we will enable the most precise constraints on cosmic inflation to date.

The Cosmic Microwave background (CMB) is the oldest source of light in existence, and our most precious resource for understanding the early history of the universe. Two vital targets for next-generation CMB experiments are B-mode polarization - a direct probe of cosmic inflation and primordial gravitational waves - and spectral distortions, which encode the energy history of the universe from redshift one million until today. In the CosmoglobeHD project, I propose to develop a joint integrated analysis framework for ground-based B-mode experiments with high spatial resolution and spectral distortion experiments with high spectral resolution, building on recent breakthroughs in the processing of CMB anisotropy satellite data. I will then use this framework to jointly analyze the upcoming state-of-the-art data from Simons Observatory (SO) with archival data from COBE/FIRAS, COBE/DIRBE, Planck, and WMAP. The main product from this analysis will be CosmoglobeHD: an absolutely calibrated high-resolution model of the radio, microwave, and sub-mm sky. This will enable cutting edge science in both fundamental cosmology and Galactic physics. The SO observations will constrain both primordial gravitational waves and cosmic birefringence to unprecedented levels, while the FIRAS analysis will reduce the frequency-domain uncertainties of the CMB spectrum by a factor of 2–5, potentially leading to the world’s first detection of large-scale non-blackbody CMB radiation. These signals probe independent aspects of ?CDM and also share many observational challenges, justifying a synergistic analysis approach. This novel integrated and Open Science analysis framework will define a new paradigm for a wide range of next-generation B-mode and spectral distortion experiments, including CMB-S4, LiteBIRD, and ESA’s Voyage 2050 spectral distortion concept.