Mapping the Primordial Universe in Unprecedented Detail with POLARBEAR

Barron Darcy, La Jolla CA

Investigators

Abstract

Darcy Barron is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the University of California, Berkeley. Barron will work on the expansion of the NSF-funded POLARBEAR project, which is mapping the cosmic microwave background (CMB) from its site in the Atacama desert in Chile. The CMB is the first light from our primordial universe, generated by the thermal glow from the Big Bang. Measurements of the CMB have been essential to our current understanding of the universe's formation, but there is still more to discover with detailed measurements of its polarization properties. The CMB field has reached an important milestone with several experiments, including POLARBEAR, making detections of a unique polarization pattern resulting from gravitational distortions. This signal is so faint that these detections required years-long "exposures" of a small patch of sky. Making detailed maps of this signal across the sky will enable significant advances in our understanding of the structure of our universe and its origins. Alongside this work, Barron will run an outreach program focused on cultivating basic research skills and interest in STEM with high school and community college students. The POLARBEAR project is expanding from one telescope observing at a single wavelength, to an array of three 3.5 meter telescopes with larger, broader bandwidth cameras. This expansion will enable a detailed survey of microwave polarization across 65% of the sky, at three different wavelengths. Barron will focus on development and observations with the new camera that will be sensitive to both the peak CMB wavelength and a shorter wavelength where Galactic emission can overwhelm the CMB signal. These simultaneous measurements will be used to monitor the Galactic contamination in the survey areas, so that the underlying primordial CMB polarization signal can be extracted. This camera will be developed and characterized at UC Berkeley before being deployed to the Chilean site. The cameras for these microwave telescopes involve complex cryogenic and electronic systems, reading out large numbers of sensitive superconducting detectors, kept at a temperature of 0.25 Kelvin. Students in the outreach program will get hands-on experience with software and hardware development through self-directed radio astronomy projects, applying the same fundamentals that go into the development of the POLARBEAR cameras.