FY13 Cosmic Frontier Experimental Research Program – Lab Review Argonne National Laboratory Background Material Program Status & Plans
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8.a Progress Report (FY11, 12, 13)In 2011, the SPT collaboration concluded a four-year survey with the SPT-SZ experiment. This survey observed 2500 square degrees in three optical bandpasses (95, 150 and 220 GHz) and achieved a depth of ~18 uK-arcmin in total intensity (or temperature) at 150 GHz. One of the recent SPT-SZ results is the first use of an SZ cluster survey to demonstrate significant improvements on the dark energy equation of state, w, and the sum of the neutrino masses, Σmν, measuring w = 0.973 ± 0.063 and Σmν< 0.28 eV at 95% confidence. The SPT-SZ has also used this survey data to publish a measurement of the primordial fine-scale CMB anisotropy power spectrum (Fig. 3). These data are sensitive to the expansion rate during recombination and thus to the number of relativistic particle species present at that epoch. This has allowed SPT to place constraints on the number of light particle species beyond the standard three neutrinos (e.g., sterile neutrinos). Combining with WMAP7, SPT-SZ measures the number of effective neutrino-like relativistic species to be Neff= 3.62 ± 0.48. This can be compared to the subsequent Planck results which measure Neff= 3.36 ± 0.33 when using only Planck data. We have also established a close connection between SPT data and ANL computational cosmology. Results include a measurement of the secondary-CMB and millimeter-wave-foreground bispectrum, where Suman Bhattacharya has played a leadership role in the analysis. In addition to the bispectrum results, Suman Bhattacharya has quantified foreground biases that induce systematic uncertainty in the CMB lensing convergence power spectrum. He used numerical simulations to generate a mock CMB sky using our  
Figure 3 Left: CMB temperature anisotropy angular power spectra at low ell as measured by Planck, WMAP, SPT, and ACT showing the remarkable precision of current CMB measurement and agreement between multiple space-based and ground-based platforms. Right: Angular power spectra measured by SPT, WMAP, and ACT up to ell~10,000 which is ~1 arcmin resolution. group’s “Coyote Universe” set of simulations. Ten snapshots equally spaced in expansion factor produce an octant CMB sky that includes lensing and other foregrounds. These simulations can evaluate the impact of the Sunyaev-Zeldovich (SZ) effect and that of star forming galaxies on measurements of the CMB lensing convergence power spectrum. In another related work, Bhattacharya is working on quantifying the cross-correlation amplitude between the SZ signal and the lensing sky using the above simulations. Work by another Argonne post-doc, Sudeep Das, is also relevant to this effort. The goal here is We have also established a close connection between SPT data and ANL computational cosmology. Results include a measurement of the secondary-CMB and millimeter-wave-foreground bispectrum, where Suman Bhattacharya has played a leadership role in the analysis. In addition to the bispectrum results, Suman Bhattacharya has quantified foreground biases that induce systematic uncertainty in the CMB lensing convergence power spectrum. He used numerical simulations to generate a mock CMB sky using our group’s “Coyote Universe” set of simulations. Ten snapshots equally spaced in expansion factor produce an octant CMB sky that includes lensing and other foregrounds. These simulations can evaluate the impact of the Sunyaev-Zeldovich (SZ) effect and that of star forming galaxies on measurements of the CMB lensing convergence power spectrum. In another related work, Bhattacharya is working on quantifying the cross-correlation amplitude between the SZ signal and the lensing sky using the above simulations. Work by another Argonne post-doc, Sudeep Das, is also relevant to this effort. The goal here is to quantify how the cross-correlation can be used to understand the astrophysical properties of galaxy groups at moderate to high redshifts. Typically, groups cannot be observed directly using CMB or X-ray telescopes and cross-correlation remains the only viable option to detect their signature. Since the CMB lensing signal originates from groups at relatively high redshifts this cross correlation of the SZ and lensing probes objects at higher redshifts. In Austral Summer 2011-12, SPT replaced the SPT-SZ receiver with the SPTpol receiver (see Fig. 4). The SPTpol deployment was a success achieving first light at the end of January 2012. This successful ANL effort was led by Clarence Chang and involved: optimization of detector design and fabrication including fine-tuning of the detector thermal conductance and normal-superconducting transition; fabrication (by Volodymyr Yefremenko) of science-grade detectors, beginning in April 2011 and ending in December 2011; and extensive testing and quality assurance (by Gensheng Wang) after which the detectors were delivered and installed onto SPT platform. The detectors have excellent on-sky performance. All devices have the desired saturation power, noise, loop gain, time constant, co-polar coupling, and cross-polar isolation. Figure 4 Image of the SPTpol focal plane. The inner detector arrays were made at NIST and observe at 150 GHz. The outer ring of detectors observe at 90 GHz and were made from scratch at ANL. ANL scientists played an active role in the development of both detector technologies. SPTpol spent its first season making ultra-deep measurements of a 100 sq deg patch of sky as its commissioning run. The first result from this season of commissioning data has recently been published and presents the first detection of CMB lensing B-modes (see Fig. 2). SPTpol has started its full 3-year survey which plans to map ~500 sq deg of sky to a depth of ~8 uK-arcmin in polarization. ANL scientists have played an active role in the low-level analysis of the incoming SPTpol data including understanding the detector relative calibrations and studies of potential ground contamination. The ANL CMB group is also actively involved in SPTpol operations traveling to the South Pole to optimize the SPTpol focal plane, conduct routine maintenance, and measure the angles of the SPTpol bolometers using a special polarized calibration source. 
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