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A quadratic maximum likelihood (QML) estimator is applied to the Wilkinson Microwave Anisotropy Probe ( WMAP) 5 year low-resolution maps to compute the cosmic microwave background angular power spectra (APS) at large scales for both temperature and polarization. Estimates and error bars for the six APS are provided up to and compared, when possible, to those obtained by the WMAP team, without finding any inconsistency. The conditional likelihood slices are also computed for the of all the six power spectra from to 10 through a pixel-based likelihood code. Both the codes treat the covariance for in a single matrix without employing any approximation. The inputs of both the codes (foreground-reduced maps, related covariances and masks) are provided by the WMAP team. The peaks of the likelihood slices are always consistent with the QML estimates within the error bars; however, an excellent agreement occurs when the QML estimates are used as a fiducial power spectrum instead of the best-fitting theoretical power spectrum. By the full computation of the conditional likelihood on the estimated spectra, the value of the temperature quadrupole is found to be less than 2σ away from the WMAP 5 year Λ cold dark matter best-fitting value. The BB spectrum is found to be well consistent with zero, and upper limits on the B modes are provided. The parity odd signals TB and EB are found to be consistent with zero. [ABSTRACT FROM AUTHOR]

The decomposition of a signal on the sphere with the steerable wavelet constructed from the second Gaussian derivative gives access to the orientation, signed-intensity and elongation of the signal's local features. In the present work, the non-Gaussianity of the Wilkinson Microwave Anisotropy Probe ( WMAP) temperature data of the cosmic microwave background (CMB) is analysed in terms of the first four moments of the statistically isotropic random fields associated with these local morphological measures, at wavelet scales corresponding to angular sizes between 27.5 arcmin and 30° on the celestial sphere. While no detection is made either in the orientation analysis or in the elongation analysis, a strong detection is made in the excess kurtosis of the signed-intensity of the WMAP data. The non-Gaussianity is observed with a significance level below 0.5 per cent at a wavelet scale corresponding to an angular size around 10°, and confirmed at neighbouring scales. This supports a previous detection of an excess of kurtosis in the wavelet coefficient of the WMAP data with the axisymmetric Mexican hat wavelet. Instrumental noise and foreground emissions are not likely to be at the origin of the excess of kurtosis. Large-scale modulations of the CMB related to some unknown systematics are rejected as possible origins of the detection. The observed non-Gaussianity may therefore probably be imputed to the CMB itself, thereby questioning the basic inflationary scenario upon which the present concordance cosmological model relies. Taking the CMB temperature angular power spectrum of the concordance cosmological model at face value, further analysis also suggests that this non-Gaussianity is not confined to the directions on the celestial sphere with an anomalous signed-intensity. [ABSTRACT FROM AUTHOR]

Wilkinson Microwave Anisotropy Probe ( WMAP) data when combined with ancillary data on free–free, synchrotron and dust allow an improved understanding of the spectrum of emission from each of these components. Here, we examine the sky variation at intermediate latitudes using a cross-correlation technique. In particular, we compare the observed emission in 15 selected sky regions to three ‘standard’ templates. The free–free emission of the diffuse ionized gas is fitted by a well-known spectrum at K and Ka band, but the derived emissivity corresponds to a mean electron temperature of ∼4000–5000 K. This is inconsistent with estimates from Galactic H ii regions although a variation in the derived ratio of Hα to free–free intensity by a factor of ∼2 is also found from region to region. The origin of the discrepancy is unclear. The anomalous emission associated with dust is clearly detected in most of the 15 fields studied. The anomalous emission correlates well with the Finkbeiner, Davis & Schlegel model 8 predictions (FDS8) at 94 GHz, with an effective spectral index between 20 and 60 GHz, of . Furthermore, the emissivity varies by a factor of ∼2 from cloud to cloud. A modestly improved fit to the anomalous dust at K band is provided by modulating the template by an estimate of the dust colour temperature, specifically . We find a preferred value , although there is a scatter from region to region. Nevertheless, the preferred index drops to zero at higher frequencies where the thermal dust emission dominates. The synchrotron emission steepens between GHz frequencies and the WMAP bands. There are indications of spectral index variations across the sky but the current data are not precise enough to accurately quantify this from region to region. Our analysis of the WMAP data indicates strongly that the dust-correlated emission at the low WMAP frequencies has a spectrum which is compatible with spinning dust; we find no evidence for a synchrotron component correlated with dust. The importance of these results for the correction of cosmic microwave background data for Galactic foreground emission is discussed. [ABSTRACT FROM AUTHOR]

We present the analysis of the first 18 months of data obtained with the COSMOSOMAS (COSMOlogical Structures On Medium Angular Scales) experiment at the Teide Observatory (Tenerife). Three maps have been obtained at 12.7, 14.7 and 16.3 GHz covering 9000 deg2 each with a resolution of ∼1° and with sensitivities 49, 59 and 115 μK beam−1, respectively. These data in conjunction with the Wilkinson Microwave Anisotropy Probe ( WMAP) first year maps have revealed that the cosmic microwave background (CMB) is the dominant astronomical signal at high galactic latitude in the three COSMOSOMAS channels with an average amplitude of (68 per cent c.l. not including calibration errors). This value is in agreement with the predicted CMB signal in the COSMOSOMAS maps using the best-fitting Λ-CDM model to the WMAP power spectrum. Cross-correlation analysis of the 408-MHz map and the COSMOSOMAS data at high galactic latitudes give values in the range from 12.7 to 16.3 GHz. Removing detected point sources in this template, reduces the amplitude of the correlated signal to 8–9 μK. The mean spectral index of the correlated signal between the 408 MHz desourced and the COSMOSOMAS maps is between −3.20 and −2.94 at which indicates that this signal is due to synchrotron emission. Cross-correlation of COSMOSOMAS data with the Diffuse Infrared Background Experiment (DIRBE) map at 100 μm shows the existence of a common signal with amplitude and in the 12.7, 14.7 and 16.3 GHz COSMOSOMAS maps at . Using the WMAP data, we find this DIRBE correlated signal rises from high to low frequencies flattening below ∼20 GHz. At higher galactic latitudes the average amplitude of the correlated signal with the DIRBE maps decreases slightly. The frequency behaviour of the COSMOSOMAS/ WMAP correlated signal with DIRBE is not compatible with the expected tendency for thermal dust. A study of the Hα emission maps do not support free–free as a major contributor to that signal. Our results provide new evidence of a Galactic foreground with properties compatible with predictions by spinning dust models. [ABSTRACT FROM AUTHOR]

We perform a blind multicomponent analysis of the Wilkinson Microwave Anisotropy Probe ( WMAP) 1-yr foreground-cleaned maps using Spectral Matching Independent Component Analysis ( smica). We provide a new estimate of the cosmic microwave background (CMB) power spectrum as well as the amplitude of the CMB anisotropies across frequency channels. We show that the CMB anisotropies are compatible with temperature fluctuations as expected from the standard paradigm. The analysis also allows us to identify and separate a weak residual Galactic emission, present significantly in the Q band outside of the Kp2 1 mask limits, and mainly concentrated at low Galactic latitudes. We produce a map of this residual component by Wiener filtering using estimated parameters. The level of contamination of CMB data by this component is compatible with the WMAP-team estimation of foreground residual contamination. In addition, the multicomponent analysis allows us to estimate jointly the power spectrum of unresolved point-source emission. [ABSTRACT FROM AUTHOR]

We present interferometric imaging at 33 GHz of the Corona Borealis supercluster, using the extended configuration of the Very Small Array. A total area of 24 deg2 has been imaged, with an angular resolution of 11 arcmin and a sensitivity of 12 mJy beam−1. The aim of these observations is to search for Sunyaev–Zel'dovich (SZ) detections from known clusters of galaxies in this supercluster and for a possible extended SZ decrement due to diffuse warm/hot gas in the intercluster medium. Hydrodynamical simulations suggest that a significant part of the missing baryons in the Local Universe may be located in superclusters. The maps constructed from these observations have a significant contribution from primordial fluctuations. We measure negative flux values in the positions of the 10 richest clusters in the region. Collectively, this implies a 3.0σ detection of the SZ effect. For two of these clusters, A2061 and A2065, we find decrements of approximately 2σ each. Our main result is the detection of two strong and resolved negative features at and , respectively, located in a region with no known clusters, near the centre of the supercluster. We discuss their possible origins in terms of primordial cosmic microwave background (CMB) anisotropies and/or SZ signals related either to unknown clusters or to a diffuse extended warm/hot gas distribution. Our analyses have revealed that a primordial CMB fluctuation is a plausible explanation for the weaker feature (probability of 37.82 per cent). For the stronger one, neither primordial CMB (probability of 0.38 per cent) nor SZ can account alone for its size and total intensity. The most reasonable explanation, then, is a combination of both primordial CMB and SZ signal. Finally, we explore what characteristics would be required for a filamentary structure consisting of warm/hot diffuse gas in order to produce a significant contribution to such a spot taking into account the constraints set by X-ray data. [ABSTRACT FROM AUTHOR]

We presentXspect, a method to obtain estimates of the angular power spectrum of the cosmic microwave background (CMB) temperature anisotropies including analytical error bars developed for theArcheopsexperiment. Cross-power spectra are computed from a set of maps and each of them is in itself an unbiased estimate of the power spectrum as long as the detector noises are uncorrelated. Then, the cross-power spectra are combined into a final temperature power spectrum with error bars analytically derived from the cross-correlation matrix.This method presents three main useful properties: (1) no estimation of the noise power spectrum is needed; (2) complex weighting schemes including sky covering and map noise properties can be easily taken into account, and corrected for, for each input map; and (3) error bars are quickly computed analytically from the data themselves with no Monte Carlo simulations involved.Xspectalso permits the study of common fluctuations between maps from different sky surveys such as CMB, Sunyaev–Zel'dovich effect or mass fluctuations from weak lensing observations. [ABSTRACT FROM AUTHOR]

We estimate the bispectrum of the Very Small Array data from the compact and extended configuration observations released in 2002 December, and compare our results with those obtained from Gaussian simulations. There is a slight excess of large bispectrum values for two individual fields, but this does not appear when the fields are combined. Given our expected level of residual point sources, we do not expect these to be the source of the discrepancy. Using the compact configuration data, we put an upper limit of 5400 on the value of fNL, the non-linear coupling parameter, at 95 per cent confidence. We test our bispectrum estimator using non-Gaussian simulations with a known bispectrum, and recover the input values. [ABSTRACT FROM AUTHOR]

A combined analysis of cosmic microwave background (CMB) and Lyman α forest data can constrain the matter power spectrum from small scales of about all the way to the horizon scale. The long lever arm and complementarity provided by such an analysis have previously led to a significant tightening of the constraints on the shape and the amplitude of the power spectrum of primordial density fluctuations. We present here a combined analysis of the WMAP three-year results with Lyman α forest data. The amplitude of the matter power spectrum σ8 and the spectral index ns inferred from the joint analysis of high- and low-resolution Lyman α forest data as analysed by Viel & Haehnelt are consistent with the new WMAP results to within 1σ. The joint analysis with the mainly low-resolution data as analysed by McDonald et al. suggests a value of σ8 that is ∼2σ higher than that inferred from the WMAP three-year data alone. The joint analysis of the three-year WMAP and the Lyman α forest data also does not favour a running of the spectral index. The best-fitting values for a combined analysis of the three-year WMAP data, other CMB data, 2-degree Field (2dF) data and the Lyman α forest data are . [ABSTRACT FROM AUTHOR]