FIRST SEASON QUIET OBSERVATIONS: MEASUREMENTS OF COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRA AT 43 GHz IN THE MULTIPOLE RANGE 25 ⩽ $\ell$ ⩽ 475

Abstract

The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43 GHz and 94 GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the cosmic microwave background (CMB). QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, over 10,000 hr of data were collected, first with the 19 element 43 GHz array (3458 hr) and then with the 90 element 94 GHz array. Each array observes the same four fields, selected for low foregrounds, together covering ≈1000 deg 2 . This paper reports initial results from the 43 GHz receiver, which has an array sensitivity to CMB fluctuations of 69 μK √ s. The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross-correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB, and EB power spectra in the multipole range = 25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3σ significance, the E-mode spectrum is consistent with the ΛCDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r = 0.35 +1.06 −0.87 . The combination of a new time-stream "double-demodulation" technique, side-fed Dragonian optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r = 0.1.

Bicep2. III. INSTRUMENTAL SYSTEMATICS

“…This polarization, which arises as a natural consequence of the same acoustic oscillations that source the temperature anisotropies (Bond & Efstathiou 1984), is curl-free (E-mode) and its angular power spectrum is uniquely predicted given the temperature (T) spectrum with the addition of no additional cosmological parameters. The agreement of the E-mode spectrum with the predictions given the best fitting T spectrum is a striking, independent confirmation of ΛCDM, modern cosmology's basic paradigm (Pryke et al 2009;QUIET Collaboration et al 2012;Barkats et al 2014;Crites et al 2014;Naess et al 2014).…”

“…BICEP2ʼs most basic guard against systematics is jackknife tests (Pryke et al 2009;Chiang et al 2010). As already described in Section 2.3, we split the data into two subsets, form T, Q, and U maps from each subset, and difference the maps.…”

Detection ofB-Mode Polarization at Degree Angular Scales by BICEP2

“…BICEP2 BB auto spectra and 95% upper limits from several previous experiments[2,40,42,43,47,[49][50][51]106]. The curves show the theory expectations for r = 0.2 and lensed-ΛCDM.…”

The Atacama Cosmology Telescope: cosmological parameters from three seasons of data

“…The current ΛCDM cosmological model provides an excellent fit to the CMB data across a wide range of angular scales, and is supported by complementary observations of large scale structure (e.g., Reid et al 2012;Ho et al 2012), Baryon Acoustic Oscillations (BAO e.g., Blake et al 2011;Anderson et al 2012;Busca et al 2013), Type Ia supernovae (e.g., Hicken et al 2009;Kessler et al 2009;Conley et al 2011), galaxy cluster measurements (e.g., Vikhlinin et al 2009;Mantz et al 2010;Rozo et al 2010;Tinker et al 2012) and observations of gravitational lensing (e.g., Massey et al 2007;Fu et al 2008;Schrabback et al 2010;Suyu et al 2010;Heymans et al 2012;Kilbinger et al 2013). While the CMB on angular scales of greater than 0.3 • has been definitively measured by the Wilkinson Microwave Anisotropy Probe (WMAP, Bennett et al 2013), a wealth of information in the CMB on smaller angular scales continues to be probed with everincreasing precision (e.g., Hedman et al 2002;Kuo et al 2007;Pryke et al 2009;Reichardt et al 2009;Sievers et al 2009;QUIET Collaboration et al 2011;Reichardt et al 2012;Das et al 2011b;Keisler et al 2011;QUIET Collaboration et al 2012). As this paper was being finalized the SPT collaboration released a new set of papers (Story et al 2012;Hou et al 2012) and the WMAP team released its final 9-year results (Bennett et al 2013;Hinshaw et al 2013).…”