Rachel Bean

Three year Wilkinson Microwave Anisotropy Probe (WMAP) observations: polarization analysis

The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the entire sky in five frequency bands between 23 and 94 GHz with polarization sensitive radiometers. We present three-year full-sky maps of the polarization and analyze them for foreground emission and cosmological implications. These observations open up a new window for understanding how the universe began and help set a foundation for future observations. WMAP observes significant levels of polarized foreground emission due to both Galactic synchrotron radiation and thermal dust emission. Synchrotron radiation is the dominant signal at l < 50 and ν . 40 GHz, while thermal dust emission is evident at 94 GHz. The least contaminated channel is at 61 GHz. We present a model of polarized foreground emission that captures the large angular scale characteristics of the microwave sky. After applying a Galactic mask that cuts 25.7% of the sky, we show that the high Galactic latitude rms polarized foreground emission, averaged over l = 4 − 6, ranges from ≈ 5 μK at 22 GHz to . 0.6 μK at 61 GHz. By comparison, the levels of intrinsic CMB polarization for a ΛCDM model with an optical depth of τ = 0.09 and assumed tensor to scalar ratio r = 0.3 are ≈ 0.3 μK for E-mode polarization and ≈ 0.03 μK for B-mode polarization. To analyze the maps for CMB polarization at l < 16, we subtract a model of the foreground emission. In the foreground corrected maps, we detect l(l+ 1)CEE l=<2−6>/2π = 0.086±0.029 (μK)2. This is interpreted as the result of rescattering of the CMB by free electrons released during reionization at zr = 10.9+2.7 −2.3 for a model with instantaneous reionization. By computing the likelihood of just the EE data as a function of τ we find τ = 0.10±0.03. When the same EE data are used in the full six parameter fit to all WMAP data (TT, TE, EE), we find τ = 0.09±0.03. We see no evidence for B-modes, limiting them to l(l+ 1)CBB l=<2−6>/2π = −0.04± 0.03 (μK)2. We perform a template fit to the E-mode and B-mode data with an approximate model for the tensor scalar ratio. We find that the limit from the polarization signals alone is r < 2.2 (95% CL) where r is evaluated at k = 0.002 Mpc−1. This corresponds to a limit on the cosmic density of gravitational waves of ΩGW h2 < 5×10−12. From the full WMAP analysis, we find r < 0.55 (95% CL) corresponding to a limit of ΩGW h2 < 1× 10−12 (95% CL). The limit on r is approaching the upper bound of predictions for some of the simplest models of inflation, r ∼ 0.3.

Probing gravity at cosmological scales by measurements which test the relationship between gravitational lensing and matter overdensity

Pengjie Zhang, 2 Michele Liguori, Rachel Bean, and Scott Dodelson 6 Shanghai Astronomical Observatory, Chinese Academy of Science, 80 Nandan Road, Shanghai, China, 200030 Joint Institute for Galaxy and Cosmology (JOINGC) of SHAO and USTC Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA, United Kingdom Department of Astronomy, Cornell University, Ithaca, NY 14853 Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510-0500 Department of Astronomy & Astrophysics, The University of Chicago, Chicago, IL 60637-1433

CMBPol Mission Concept Study Probing Ination with CMB Polarization

We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes of the physics of ination. We focus on the prospects for using CMB measurementsWe summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes of the physics of inflation. We focus on the prospects for using CMB measurements to differentiate various inflationary mechanisms. In particular, a detection of primordial B‐mode polarization would demonstrate that inflation occurred at a very high energy scale, and that the inflaton traversed a super‐Planckian distance in field space. We explain how such a detection or constraint would illuminate aspects of physics at the Planck scale. Moreover, CMB measurements can constrain the scale‐dependence and non‐Gaussianity of the primordial fluctuations and limit the possibility of a significant isocurvature contribution. Each such limit provides crucial information on the underlying inflationary dynamics. Finally, we quantify these considerations by presenting forecasts for the sensitivities of a future satellite experiment to the inflationary parameters.

Dynamics of linear perturbations in f(R) gravity

We consider predictions for structure formation from modifications to general relativity in which the Einstein-Hilbert action is replaced by a general function of the Ricci scalar. We work without fixing a gauge, as well as in explicit popular coordinate choices, appropriate for the modification of existing cosmological code. We present the framework in a comprehensive and practical form that can be directly compared to standard perturbation analyses. By considering the full evolution equations, we resolve perceived instabilities previously suggested, and instead find a suppression of perturbations. This result presents significant challenges for agreement with current cosmological structure formation observations. The findings apply to a broad range of forms of

Probing dark energy perturbations: The Dark energy equation of state and speed of sound as measured by WMAP

f(R)

Three-Year Wilkinson Microwave Anisotropy Probe (WMAP)* Observations: Beam Profiles, Data Processing, Radiometer Characterization, and Systematic Error Limits

for which the modification becomes important at low curvatures, disfavoring them in comparison with the

Are Chaplygin gases serious contenders to the dark energy throne

\ensuremath{\Lambda}\mathrm{CDM}

Current constraints on the cosmic growth history

scenario. As such, these results provide a powerful method to rule out a wide class of modified gravity models aimed at providing an alternative explanation to the dark energy problem.

Comparing Brane Inflation to WMAP

We review the implications of having a nontrivial matter component in the Universe and the potential for detecting such a component through the matter power spectrum and integrated Sachs-Wolfe effect. We adopt a phenomenological approach and consider the mysterious dark energy to be a cosmic fluid. It is thus fully characterized, up to linear order, by its equation of state and its speed of sound. Whereas the equation of state has been widely studied in the literature, less interest has been devoted to the speed of sound. Its observational consequences come predominantly from very large scale modes of dark matter perturbations

Constraining Interactions in Cosmology's Dark Sector

(kl0.01h{\mathrm{Mpc}}^{\ensuremath{-}1}).