A theory of a spot

Clusters of galaxies can distort the cosmological signal in the cosmic microwave background (CMB) temperature fluctuations maps through the Sunyaev-Zel'dovich (SZ) effect. The analysis of this effect, which depends on the properties of the cluster population and its spatial distribution, could therefore be used to constrain the cluster mass function and its evolution. We present the global SZ effect expected for a cluster population extending to z = 0.2, z = 0.5, and z = 0.8, for random and nonrandom spatial distributions. The local population (up to z = 0.2) was built according to current results and in agreement with the XBACs data for the high-mass fraction of the cluster mass distribution. The resulting signal from the global SZ effect is well under the noise level of the Wilkinson Microwave Anisotropy Probe (WMAP) data for both distributions. The extension of the population to higher redshifts was done keeping the same mass distribution (without evolution). For the Poissonian distribution only at multipoles l ≥ 300 in the z = 0.8 case, the effects are over the noise level of the WMAP data. However, for the more realistic, nonrandom distribution case that signal would be detectable in the WMAP maps for multipoles higher than l = 100 at z = 0.5 and for nearly all multipoles at z = 0.8, in clear conflict with the data. The analysis of high-quality CMB data, as those expected from the Planck mission, will allow us to determine the contribution from the cluster population and to determine the evolution of clusters even at low redshift.

The Wilkinson Microwave Anisotropy Probe (WMAP) is currently mapping the temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation on the full sky at five microwave frequencies. We summarize the major scientific results from the analysis of the first-year WMAP data, released on 11 February 2003: (1) the WMAP data alone fits a standard cosmological model, giving precise determinations of its six parameters; (2) the universe was reionized very early on in its history; (3) a joint analysis of WMAP data with smaller scale ground-based CMB experiments and large-scale structure data yields improved constraints on the geometry of the universe, the dark energy equation of state, the energy density in stable neutrino species and the inflationary paradigm.

We present a new procedure to measure the large-scale carbon monoxide (CO) emissions across cosmic history. As a tracer of large-scale structure (LSS), the CO gas content as a function of redshift can be quantified by its three-dimensional fluctuation power spectra. Furthermore, cross-correlating CO emission with other LSS tracers offers a way to measure the emission as a function of scale and redshift. Here we introduce the model relevant for such a cross-correlation measurement between CO and other LSS tracers, and between different CO rotational lines. We propose a novel use of cosmic microwave background (CMB) data and attempt to extract redshifted CO emissions embedded in the Wilkinson Microwave Anisotropy Probe (WMAP) data set. We cross-correlate the all-sky WMAP7 data with LSS data sets, namely, the photometric quasar sample and the luminous red galaxy sample from the Sloan Digital Sky Survey Data Releases 6 and 7, respectively. We are unable to detect a cross-correlation signal with either CO(1–0) or CO(2–1) lines, mainly due to the instrumental noise in the WMAP data. However, we are able to rule out models more than three times greater than our more optimistic model. We discuss the cross-correlation signal from the thermal Sunyaev–Zeldovich effect and dust as potential contaminants, and quantify their impact for our CO measurements. We discuss forecasts for current CMB experiments and a hypothetical future CO-focused experiment, and propose to cross-correlate CO temperature data with the Hobby–Eberly Telescope Dark Energy Experiment Lyα-emitter sample, for which a signal-to-noise ratio of 58 is possible.

Wilkinson Microwave Anisotropy Probe (WMAP) observations have accurately determined the position of the first two peaks and dips in the cosmic microwave background (CMB) temperature power spectrum. These encode information on the ratio of the distance to the last scattering surface to the sound horizon at decoupling. However prerecombination processes can contaminate this distance information. In order to assess the amplitude of these effects, we use the WMAP data and evaluate the relative differences of the CMB peak and dip multipoles. We find that the position of the first peak is largely displaced with respect to the expected position of the sound horizon scale at decoupling. In contrast, the relative spacings of the higher extrema are statistically consistent with those expected from perfect harmonic oscillations. This provides evidence for a scale dependent phase shift of the CMB oscillations which is caused by gravitational driving forces affecting the propagation of sound waves before recombination. By accounting for these effects we have performed a Markov Chain Monte Carlo likelihood analysis of the location of WMAP extrema to constrain, in combination with recent BAO data, a constant dark energy equation of state parameter $w$. For a flat universe we find a strong $2\ensuremath{\sigma}$ upper limit $wl\ensuremath{-}1.10$, and including the Hubble Space Telescope prior, we obtain $wl\ensuremath{-}1.14$, which is only marginally consistent with limits derived from the Supernova Legacy Survey sample. On the other hand, we infer larger limits for nonflat cosmologies. From the full CMB likelihood analysis, we also estimate the values of the shift parameter $R$ and the multipole ${l}_{a}$ of the acoustic horizon at decoupling for several cosmologies, to test their dependence on model assumptions. Although the analysis of the full CMB spectra should always be preferred, using the position of the CMB peaks and dips provides a simple and consistent method for combining CMB constraints with other data sets.

Temperature fluctuations of the cosmic microwave background radiation: A case of non-extensivity?

Accurate measurements of the angular power spectrum of cosmic microwave background (CMB) radiation have lead to a marked improvement in the estimates of different cosmological parameters. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. We present the estimation of the CMB angular power spectrum from the multifrequency observations of the Wilkinson Microwave Anisotropy Probe (WMAP) using a novel model-independent method. The primary results of WMAP are the observations of the CMB in 10 independent difference assemblies (DAs) that have uncorrelated noise. Our method utilizes the maximum information available within the WMAP data by linearly combining all the DA maps in order to remove foreground contamination and by estimating the power spectrum from cross-power spectra of clean maps with independent noise. We compute 24 cross-power spectra that are the basis of the final power spectrum. The binned average power matches the WMAP team's published power spectrum closely. A small systematic difference at large multipoles is accounted for by the correction for the expected residual power from unresolved point sources. The correction is small and significantly tempered. Previous estimates have depended on foreground templates built using extraneous observational input. This is the first demonstration that the CMB angular spectrum can be reliably estimated with precision from a self-contained analysis of the WMAP data.

We build template maps for the polarized Galactic synchrotron emission on large angular scales (7° full width at half maximum), in the 20-90 GHz microwave range, by using Wilkinson Microwave Anisotropy Probe (WMAP) data. The method, presented in recent work, requires a synchrotron total-intensity survey and the polarization horizon to model the polarized intensity and a starlight polarization map to model polarization angles. The basic template is obtained directly at 23 GHz with about 94 per cent sky coverage by using the synchrotron map released by the WMAP team. Extrapolations to 32, 60 and 90 GHz are performed by computing a synchrotron spectral-index map, which strongly reduces previous uncertainties in passing from low (1.4 GHz) to microwave frequencies. Differing from low-frequency data, none of our templates present relevant structures out of the Galactic plane. Our map at 90 GHz suggests that the synchrotron emission at high Galactic latitudes is low enough to allow robust detection of the E-mode component of the cosmological signal on large scale, even in models with low reionization (r = 0.05). Detection of the weaker B-mode on the largest scales (l 0.1. For lower levels of the gravitational-wave background the B-mode seems to be accessible only at the l ∼ 100 peak and in selected low-synchrotron emission areas.

We discuss the nature of the possible high-l excess in the cosmic microwave background (CMB) anisotropy power spectrum observed by the Cosmic Background Imager (CBI). We probe the angular structure of the excess in the CBI deep fields and investigate whether it could be due to the scattering of CMB photons by hot electrons within clusters, which is the Sunyaev-Zel'dovich (SZ) effect. We estimate the density fluctuation parameters for amplitude, σ8, and shape, Γ, from CMB primary anisotropy data and other cosmological data. We use the results of two separate hydrodynamic codes for ΛCDM cosmologies, consistent with the allowed σ8 and Γ values, to quantify the expected contribution from the SZ effect to the band powers of the CBI experiment and pass simulated SZ effect maps through our CBI analysis pipeline. The result is very sensitive to the value of σ8 and is roughly consistent with the observed power if σ8 ≈ 1. We conclude that the CBI anomaly could be a result of the SZ effect for the class of ΛCDM concordance models if σ8 is in the upper range of values allowed by current CMB and large-scale structure data.

H olding his 3-month-old son, Joshua, in his arms, cosmologist David N. Spergel will proudly watch the launch next week of a NASA satellite that he helped father. The satellite will record the remnant glow from the infant universe in greater detail than ever before. Even before the Microwave Anisotropy Probe satellite gets off the ground, however, Spergel and his colleagues have hatched a plan to examine that early light in a dramatically different way. The satellite will continue the practice of treating the cosmic microwave background (CMB)-the glow left over from the Big Bang-as a snapshot of the early universe. Taking a new perspective, Spergel and his colleagues propose to use that radiation as a flashlight to illuminate the evolution of structure in the universe over its 13-billion-year history. That evolution began with the condensation of gas clouds into fledgling galaxies and continued with production of the first stars and the assembly of galaxies into mammoth clusters. To realize this ambitious idea, Spergel and several other astronomers intend to examine the subtle markings acquired by the CMB as it traversed billions of lightyears to reach Earth. Like a weary traveler who has picked up dust from each country he's visited, the microwave background has been marked by all the cosmic architecture that it has encountered. As it streams across the universe, the CMB lighting up the past between here and there, says Spergel, who is based at Princeton University. The photons in the CMB have been traveling freely through space ever since the universe was about 300,000 years old. And a lot of things happened to them along the way, Spergel notes You have lots of imprints on the microwave background from the emergence of structure. Those imprints show up on a much finer scale than that of the primordial features painted onto the CMB by the Big Bang itself. Those relatively large hot and cold spots in the CMB, which the spaceborne Microwave Anisotropy Probe will detect, represent the seeds from which galaxies and galaxy clusters ultimately arose. Galaxies and galaxy clusters buffet the CMB photons coursing through them. These interactions generate hot and cold spots that differ by only a millionth of a degree or so from the average temperature of the microwave background, a chilly 2.76 kelvins. That's one-tenth as small as the temperature fluctuations imprinted on the CMB by the tumultuous conditions in the nascent universe. The tinier, post-Big Bang variations also occur on spatial scales only one-third the size of the primordial hot and cold spots that the Microwave Anisotropy Probe can discern. The sensitive detectors required to study these tiny variations, which theo-

The Wilkinson Microwave Anisotropy Probe (WMAP) measures anisotropy or temperature differences in the Cosmic Microwave Background (CMB) radiation with high angular resolution and sensitivity, yielding unprecedented accuracy. To achieve this measurement, WMAP’s back-to-back Gregorian telescopes focus microwave radiation into 20 feed horns connected to 10 differential microwave radiometers. Proper alignment of the telescope reflectors, feed horns, and radiometers at flight temperatures was essential to the mission success. This paper will present the WMAP instrument metrology requirements and associated challenges, discuss the opto-mechanical tooling utilized to accomplish these objectives, and then give an overview of the metrology effort. The WMAP instrument integration effort included the following key metrology tasks: alignment and clocking of 20 microwave feed horns and mating microwave differencing assemblies within a focal plane assembly; alignment of a pair of primary and secondary reflectors composing back-to-back Gregorian telescopes; and the placement of the focal plane assembly and reflector system relative to each other, and as a unit on the spacecraft. WMAP environmental test metrology efforts included: reflector and truss thermal stability at 80 K; reflector and feed horn position verification at 90 K, and pre and post vibration and acoustic test reflector and feed horn position verification. The WMAP instrument integration and test objectives required the use of a photogrammetric camera, a laser tracker, a portable coordinate measuring machine (PCMM), and theodolites utilizing an electronic theodolite metrology system (ETMS) and autocollimation. The synergy of these metrology systems facilitated the successful characterization of the WMAP scientific instrument mechanical performance data at room temperature and flight temperatures, and correlation of the data to the analytical model. WMAP was launched on July 1, 2001, and flight data has confirmed the proper on-orbit instrument alignment was achieved.

In this paper we use the current and future cosmic microwave background (CMB) experiments to test the Charge-Parity-Time Reversal (CPT) symmetry. We consider a CPT-violating interaction in the photon sector $\mathcal{L}_{\rm cs}\sim p_\mu A_\nu \tilde{F}^{\mu\nu}$ which gives rise to a rotation of the polarization vectors of the propagating CMB photons. By combining the nine-year WMAP, BOOMERanG 2003 and BICEP1 observations, we obtain the current constraint on the isotropic rotation angle $\bar{\alpha} = -2.12 \pm 1.14$ ($1\sigma$), indicating an about $2\sigma$ significance of the CPT violation. Here, we particularly take the systematic errors of CMB measurements into account. Then, we study the effects of the anisotropies of the rotation angle [$\Delta{\alpha}({\bf \hat{n}})$] on the CMB polarization power spectra in detail. Due to the small effects, the current CMB polarization data can not constrain the related parameters very well. We obtain the 95\% C.L. upper limit of the variance of the anisotropies of the rotation angle $C^\alpha(0) < 0.035$ from all the CMB datasets. More interestingly, including the anisotropies of rotation angle could lower the best fit value of $r$ and relax the tension on the constraints of $r$ between BICEP2 and Planck. Finally, we investigate the capabilities of future Planck polarization measurements on $\bar{\alpha}$ and $\Delta{\alpha}({\bf \hat{n}})$. Benefited from the high precision of Planck data, the constraints of the rotation angle can be significantly improved.

We extend the standard theory of cosmological perturbations to homogeneous butanisotropic universes. We present an exhaustive computation for the case of a Bianchi Imodel, with a residual isotropy between two spatial dimensions, which is undergoingcomplete isotropization at the onset of inflation; we also show how the computation can befurther extended to more general backgrounds. In the presence of a single inflaton field,there are three physical perturbations (precisely as in the isotropic case), whichare obtained (i) by removing gauge and non-dynamical degrees of freedom, and(ii) by finding the combinations of the remaining modes in terms of which thequadratic action of the perturbations is canonical. The three perturbations, whichlater in the isotropic regime become a scalar mode and two tensor polarizations(gravitational wave), are coupled to each other already at the linearized level during theanisotropic phase. This generates non-vanishing correlations between different modes ofthe cosmic microwave background (CMB) anisotropies, , which can be particularly relevant at large scales (and, potentially, be related to the largescale anomalies in the WMAP (Wilkinson Microwave Anisotropy Probe) data). As anexample, we compute the spectrum of the perturbations in this Bianchi I geometry,assuming that the inflaton is in a slow roll regime also in the anisotropic phase. For thissimple set-up, fixing the initial conditions for the perturbations appears more difficult thanin the standard case, and additional assumptions seem to be needed to provide predictionsfor the CMB anisotropies.

A topologically finite universe, smaller than the observable horizon, will have circles-in-the-sky: pairs of circles around which the temperature fluctuations in the cosmic microwave background are correlated. The circles occur along the intersection of copies of the spherical surface of last scattering. For any observer moving with respect to the microwave background, the circles will be deformed into ovals. The ovals will also be displaced relative to the direction they appear in a comoving frame. The displacement is the larger of the two effects, being proportional to the velocity. For the Earth's motion, the effect is on the order of 0.14\ifmmode^\circ\else\textdegree\fi{} at the very worst. This can affect all pattern-based searches for the topology of the universe. In particular, although the deviation is too small to impact the search for circles in the Wilkinson microwave anisotropy probe (WMAP) data, higher-resolution searches for circle pairs will need to compensate for this effect.

Simulated observations of a $10\dg \times 10\dg$ field by the Microwave Anisotropy Probe (MAP) are analysed in order to separate cosmic microwave background (CMB) emission from foreground contaminants and instrumental noise and thereby determine how accurately the CMB emission can be recovered. The simulations include emission from the CMB, the kinetic and thermal Sunyaev-Zel'dovich (SZ) effects from galaxy clusters, as well as Galactic dust, free-free and synchrotron. We find that, even in the presence of these contaminating foregrounds, the CMB map is reconstructed with an rms accuracy of about 20 $\mu$K per 12.6 arcmin pixel, which represents a substantial improvement as compared to the individual temperature sensitivities of the raw data channels. We also find, for the single $10\dg \times 10\dg$ field, that the CMB power spectrum is accurately recovered for $\ell \la 600$.

We improve standard big bang nucleosynthesis (SBBN) calculations by taking into account new nuclear physics analyses (the 2003 work of Descouvemont and coworkers). Using a Monte Carlo technique, we calculate the abundances of light nuclei (D, 3He, 4He, and 7Li) versus the baryon-to-photon ratio. The results concerning Ωbh2 are compared with relevant astrophysical and cosmological observations: the abundance determinations in primitive media and the results from cosmic microwave background (CMB) experiments, especially the Wilkinson Microwave Anisotropy Probe (WMAP) mission. Consistency between WMAP, SBBN results, and D/H data strengthens the deduced baryon density and has interesting consequences on cosmic chemical evolution. A significant discrepancy between the calculated 7Li abundance deduced from WMAP and the Spite plateau is clearly revealed. To explain this discrepancy, three possibilities are invoked: systematic uncertainties on the Li abundance, surface alteration of Li in the course of stellar evolution, or poor knowledge of the reaction rates related to 7Be destruction. In particular, the possible role of the up to now neglected 7Be(d, p)2 α and 7Be(d, α)5Li reactions is considered. Another way to reconcile these results coming from different horizons consists of invoking new, speculative primordial physics that could modify the nucleosynthesis emerging from the big bang and perhaps the CMB physics itself. The impressive advances in CMB observations provide a strong motivation for more efforts in experimental nuclear physics and high-quality spectroscopy to keep SBBN in pace.