Probing Cosmology with Diffuse Background Radiation Observations

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Cosmology is the study of the physical universe and our place in it. The questions being addressed are profound: How old is the universe? How did it begin? How will it end? Is it finite or infinite? Just over a decade ago we had only rudimentary knowledge of the age and fate of our universe. Today, thanks to precise observations from an array of high-technology instrumentation, we know the age of the universe to better than 1%: 13.77 billion years. We know the contents of the universe are dominated by dark matter (24%) and dark energy (71%). Ordinary atomic matter makes up only 4.6% of the universe. To the best of our knowledge, the universe is infinite (or at least very large) and it will continue expanding forever, indeed at an ever-faster rate. The fullsky maps of the cosmic microwave background (CMB) radiation produced by NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and ESA's Planck Surveyor Mission played a pivotal role in these advances. As a founding member of the WMAP team I have spent most of my career studying the CMB. I propose to continue these very productive studies Since moving to Canada in 2011, I have helped form a new observational program to study the nature of the dark energy in more detail. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a new "digital" radio telescope being built in British Columbia by a group of Canadian scientists (myself included). CHIME will take a CMB-like approach to measuring dark energy by observing the Baryon Acoustic Oscillation (BAO) scale in diffuse neutral hydrogen (HI) gas via its 21 cm emission. By focusing on diffuse emission, CHIME can survey a vastly larger volume of space than has been previously possible. CHIME is made feasible thanks to rapid advances in radio amplifiers (driven by the cell phone industry) and computing with graphics processing units (driven by the gaming industry). The survey produced by CHIME will allow us to measure the expansion history of the universe and discern if the dark energy deviates from a cosmological constant, a form of vacuum energy first posited by Einstein nearly 100 years ago. In addition to fielding a new telescope, I will continue to pursue a vigorous program of data analysis from more recent CMB experiments. For example, with a group of WMAP team members, we are studying the Planck mission data and comparing it to other pertinent cosmological data. Our focus is to assess the reliability of the Planck data and to understand if all sources of systematic error have been understood and characterized. I am also using the Sunyaev-Zeldovich effect to study the distribution of gas around galaxies to try to understand if violent "feedback" processes early in a galaxy's history act to expel gas from it and quench star formation.