Probing fundamental physics by measuring the cosmic microwave background from 5200 meters

Michael Niemack (National Institute of Standards & Technology, Boulder)
Event Date and Time: 
Mon, 2011-11-21 16:00 - 17:00
Hennings 318
Local Contact: 
Jaymie Matthews and Mark Halpern
Intended Audience: 
Recent measurements of the cosmic microwave background (CMB) have played a major role in the development of the "standard model" of cosmology: a universe dominated by dark energy and dark matter. However, fundamental aspects of the cosmos remain elusive, such as the nature of dark energy and dark matter and whether an inflationary epoch occurred in the first 10^(-30) seconds after the big bang. We are helping to address these issues with high precision, high-resolution measurements of the CMB temperature and polarization. The 6-meter Atacama Cosmology Telescope (ACT) is located at 5200 meters in northeastern Chile, and was used to observe the CMB temperature fluctuations on arcminute scales for three years of observations. First light was observed with ACT using three arrays of superconducting transition-edge sensor bolometers (operated at 148, 218, and 277 GHz) in 2008. These measurements led to the discovery of new galaxy clusters, improved constraints on cosmological parameters, and the first detection of the CMB gravitational lensing power spectrum. Will will soon deploy two polarization-sensitive instruments at the ACT site to probe the CMB on both large and small angular scales using new superconducting polarimeter arrays under development at NIST. The Atacama B-mode Search (ABS) will probe GUT energy scales by searching for the "smoking gun of inflation" - the signature of inflationary gravity waves in the CMB polarization. The ACTPol receiver will add polarization sensitivity to ACT (as well as ~4x the temperature sensitivity) enabling a wealth of new science objectives. By making high precision measurements of the power spectra of the polarization anisotropies and gravitational lensing of the CMB, ACTPol will provide strong constraints on the inflationary potential, the sum of the neutrino masses, and early dark energy. Cross-correlating these measurements with optical observations will strengthen constraints on the neutrino mass sum and dark energy, in addition to providing optical counterparts for the ~10^3 galaxy clusters that will be detected by ACTPol. We will describe the CMB science, observations, and instrumentation.
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