We detect the kinematic Sunyaev-Zel'dovich (kSZ) effect with a statistical significance of 4.2σ by combining a cluster catalogue derived from the first year data of the Dark Energy Survey (DES) with CMB temperature maps from the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) Survey. This measurement is performed with a differential statistic that isolates the pairwise kSZ signal, providing the first detection of the large-scale, pairwise motion of clusters using redshifts derived from photometric data. By fitting the pairwise kSZ signal to a theoretical template we measure the average central optical depth of the cluster sample, τ e = (3.75 ± 0.89) · 10 −3 . We compare the extracted signal to realistic simulations and find good agreement with respect to the signal-to-noise, the constraint onτ e , and the corresponding gas fraction. High-precision measurements of the pairwise kSZ signal with future data will be able to place constraints on the baryonic physics of galaxy clusters, and could be used to probe gravity on scales 100 Mpc.

We investigate the hemispherical power asymmetry in the cosmic microwave background on small angular scales. We find an anomalously high asymmetry in the multipole range = 601−2048, with a naive statistical significance of 6.5σ. However, we show that this extreme anomaly is simply a coincidence of three other effects, relativistic power modulation, edge effects from the mask applied, and inter-scale correlations. After correcting for all of these effects, the significance level drops to ∼ 1σ, i.e., there is no anomalous intrinsic asymmetry in the small angular scales. Using this null result, we derive a constraint on a potential dipolar modulation amplitude, A(k) < 0.0045 on the ∼ 10 Mpc-scale, at 95% C.L. This new constraint must be satisfied by any theoretical model attempting to explain the hemispherical asymmetry at large angular scales.The statistical properties of the anisotropies in the temperature of the cosmic microwave background (CMB) possess a wealth of cosmological information. There are many potential methods to extract this information, each of which will provide statistical information about a particular aspect of cosmology. If the universe is statistically homogeneous and isotropic, and the primordial temperature anisotropies follow a Gaussian distribution, then the angular power spectrum is sufficient to describe all the statistical properties of these anisotropies. Therefore, in such a universe, a measurement of the angular power spectrum would also provide all the cosmological information available within the CMB temperature anisotropies.The angular power spectrum of the measured CMB temperature anisotropies fits its theoretical prediction from the statistically Gaussian, homogeneous and isotropic, Λ cold dark matter (ΛCDM) standard model, remarkably well [1]. From the angular power spectrum alone, no strong evidence is found for the existence of, e.g., additional matter or radiation species, isocurvature in the primordial fluctuations, or a primordial spectrum of curvature fluctuations that is not described by a power-law. However, some anomalies have been found using other statistical observables, i.e. features in the observed sky that have a low probability of occurring in the ΛCDM model. These anomalies are predominantly seen on the largest angular scales. An overview of anomalies seen in the WMAP data is presented in [2,3]. Most of the anomalies seen in the WMAP data have been confirmed with the new Planck data [4].One such anomaly is the 'hemispherical power asymmetry': Eriksen et al [5] and Hansen et al [6] found that the angular power spectrum of the CMB temperature anisotropies, from the 1-year WMAP data, appears itself to be anisotropic. In particular it was found that, in the low multipole range = 2 − 40, the hemisphere centred at Galactic coordinates (l, b) = (237 • , −20 • ) has significantly more power than the one opposite on the sky. A possible connection between this hemispherical asymmetry and an alignment between the quadrupole and octopole was pointed out in [7]. It has als...

Future data from galaxy redshift surveys, combined with high-resolutions maps of the cosmic microwave background, will enable measurements of the pairwise kinematic Sunyaev-Zel'dovich (kSZ) signal with unprecedented statistical significance. This signal probes the matter-velocity correlation function, scaled by the average optical depth (τ) of the galaxy groups and clusters in the sample, and is thus of fundamental importance for cosmology. However, in order to translate pairwise kSZ measurements into cosmological constraints, external constraints on τ are necessary. In this work, we present a new model for the intracluster medium, which takes into account star formation, feedback, non-thermal pressure, and gas cooling. Our semi-analytic model is computationally efficient and can reproduce results of recent hydrodynamical simulations of galaxy cluster formation. We calibrate the free parameters in the model using recent X-ray measurements of gas density profiles of clusters, and gas masses of groups and clusters. Our observationally calibrated model predicts the average 500 t (i.e., the integrated τ within a disk of size R 500 ) to better than 6% modeling uncertainty (at 95% confidence level). If the remaining uncertainties associated with other astrophysical uncertainties and X-ray selection effects can be better understood, our model for the optical depth should break the degeneracy between optical depth and cluster velocity in the analysis of future pairwise kSZ measurements and improve cosmological constraints with the combination of upcoming galaxy and CMB surveys, including the nature of dark energy, modified gravity, and neutrino mass.