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STScI Webcast

2018 Spring Science Colloquia

Probing the Universe with High-Resolution Cosmic Microwave Background Maps

Presented by: Suzanne Staggs (Princeton University)
Category: Science Colloquia   Duration: 1 hour   Broadcast date: February 14, 2018
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Famously, the rich angular power spectrum of the intensity of the cosmic microwave background (CMB) reveals the state of the universe a mere 10^{13} s after the big bang. In its fine-angular scale details, the CMB also encodes details of the CMB’s interactions with the rest of the universe in the subsequent 4^{17} s. The CMB is slightly polarized by Thomson scattering when there is any local quadrupolar anisotropy in the distribution of the scattering electron population. A primordial gravitational wave (PGW) background would imprint odd-parity polarizations patterns in the CMB polarization at very large angular scales, known as B-modes. Detection of PGWs would have an enormous impact on our understanding of the universe in its earliest instants (as early as 10^{-32} s): inflation is the only proposed primordial source for the as-yet undetected B-modes. At small angular scales, the CMB temperature and polarization maps provide fresh cosmological information, in part because of their sensitivity to the history of the growth rate of structures by gravitational collapse in the expanding universe. The Atacama Cosmology Telescope (ACT) is a special-purpose 6m telescope situated at 17,000 ft in the dry Atacama Desert of northern Chile, at a latitude of 23 degrees South. ACT’s millimeter-wave detectors measure both polarization and intensity at very fine angular scales (arcminutes). I will describe the ACT instrument and its data in the context of other ongoing and proposed CMB measurements, their scientific impact, and the potential discovery space.