Wilkinson Microwave Anisotropy Probe Data Research Articles

Constraints on a mixed inflaton and curvaton scenario for the generation of the curvature perturbation

We consider a supersymmetric grand unified model which naturally solves the strong CP and mu problems via a Peccei-Quinn symmetry and leads to the standard realization of hybrid inflation. We show that the Peccei-Quinn field of this model can act as curvaton. In contrast to the standard curvaton hypothesis, both the inflaton and the curvaton contribute to the total curvature perturbation. The model predicts an isocurvature perturbation too which has mixed correlation with the adiabatic one. The cold dark matter of the universe is mostly constituted by axions plus a small amount of lightest sparticles. The predictions of the model are confronted with the Wilkinson microwave anisotropy probe and other cosmic microwave background radiation data. We analyze two representative choices of parameters and derive bounds on the curvaton contribution to the adiabatic perturbation. We find that, for the choice which provides the best fitting of the data, the curvaton contribution to the adiabatic amplitude must be smaller than about 67% (at 95% confidence level). The best-fit power spectra are dominated by the adiabatic part of the inflaton contribution. We use Bayesian model comparison to show that this choice of parameters is disfavored with respect to the pure inflaton scale-invariant case with odds of 50 to 1. For the second choice of parameters, the adiabatic mode is dominated by the curvaton, but this choice is strongly disfavored relative to the pure inflaton scale-invariant case (with odds of 10^7 to 1). We conclude that in the present framework the perturbations must be dominated by the adiabatic component from the inflaton.

Bayesian Power Spectrum Analysis of the First-Year Wilkinson Microwave Anisotropy Probe Data

We present the first results from a Bayesian analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) first-year data using a Gibbs sampling technique. Using two independent, parallel supercomputer codes, we analyze the WMAP Q, V, and W bands. The analysis results in a full probabilistic description of the information the WMAP data set contains about the power spectrum and the all-sky map of the cosmic microwave background anisotropies. We present the complete probability distributions for each Cl, including any non-Gaussianities of the power spectrum likelihood. While we find good overall agreement with the previously published WMAP spectrum, our analysis uncovers discrepancies in the power spectrum estimates at low-l multipoles. For example, we claim that the best-fit ΛCDM model is consistent with the C2 inferred from our combined Q+V+W analysis, with a 10% probability of an even larger theoretical C2. Based on our exact analysis, we can therefore attribute the low-quadrupole issue to a statistical fluctuation.

Modular invariant soft breaking, WMAP, dark matter, and sparticle mass limits

An analysis of soft breaking under the constraint of modular invariance is given. The role of dilaton and moduli dependent front factors in achieving a modular invariant ${V}_{\mathrm{s}\mathrm{o}\mathrm{f}\mathrm{t}}$ is emphasized. Further, it is shown that in string models $\mathrm{tan}\ensuremath{\beta}$ is no longer a free parameter but is determined in terms of ${\ensuremath{\alpha}}_{\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{i}\mathrm{n}\mathrm{g}}$ and the other soft parameters by the constraints of modular invariance and radiative electroweak symmetry breaking. The above framework is then used to analyze the neutralino relic density consistent with the Wilkinson Microwave Anisotropy Probe (WMAP) data at self-dual points in the K\"ahler and complex structure moduli. One finds that the combined set of constraints arising from modular invariant soft breaking, radiative electroweak symmetry breaking, and WMAP lead to upper limits on sparticle masses for $\ensuremath{\mu}>0$. These limits are investigated for a class of models and found to lie within reach of the Tevatron and the Large Hadron Collider. Further, an analysis of the neutralino-proton cross section shows that dark matter in these models can be explored in CDMS (Soudan), GENIUS, and ZEPLIN. While the analysis is carried out within the general framework of heterotic strings, the possibility that the results of the analysis may extend to a broader class of string models, such as models based on intersecting D branes, is also discussed.

The Angular Power Spectrum of the First-Year Wilkinson Microwave Anisotropy Probe Data Reanalyzed

We measure the angular power spectrum of the Wilkinson Microwave Anisotropy Probe (WMAP) first-year temperature anisotropy maps. We use the Spatially Inhomogeneous Correlation Estimator (SpICE) to estimate Cl's for multipoles l = 2-900 from all possible cross-correlation channels. Except for the map-making stage, our measurements provide an independent analysis of that by G. Hinshaw et al. Despite the different methods used, there is virtually no difference between the two measurements for l 700; the highest l's are still compatible within 1 σ errors. We use a novel intrabin variance method to constrain Cl errors in a model-independent way. Simulations show that our implementation of the technique is unbiased within 1% for l 100. When applied to WMAP data, the intrabin variance estimator yields diagonal errors ~10% larger than those reported by the WMAP team for 100 < l < 450. This translates into a 2.4 σ detection of systematics, since no difference is expected between the SpICE and the WMAP team estimator window functions in this multipole range. With our measurement of the Cl's and errors, we get a χ2 per degree of freedom (dof) of 1.042 for a best-fit ΛCDM model, which has a 14% probability, whereas the WMAP team obtained χ2/dof = 1.066, which has a 5% probability. We assess the impact of our results on cosmological parameters using Markov chain Monte Carlo simulations. From WMAP data alone, assuming spatially flat power-law ΛCDM models, we obtain the reionization optical depth τ = 0.145 ± 0.067, spectral index ns = 0.99 ± 0.04, Hubble constant h = 0.67 ± 0.05, baryon density Ωbh2 = 0.0218 ± 0.0014, cold dark matter density ΩCDMh2 = 0.122 ± 0.018, and σ8 = 0.92 ± 0.12, consistent with a reionization redshift zre = 16 ± 5 (68% CL).

Cross-correlation of CMB with large-scale structure: Weak gravitational lensing

We present the results of a search for gravitational lensing of the cosmic microwave background (CMB) in cross-correlation with the projected density of luminous red galaxies. The CMB lensing reconstruction is performed using the first year of Wilkinson Microwave Anisotropy Probe data, and the galaxy maps are obtained using the Sloan Digital Sky Survey imaging data. We find no detection of lensing; our constraint on the galaxy bias derived from the galaxy-convergence cross-spectrum is ${b}_{g}=1.81\ifmmode\pm\else\textpm\fi{}1.92$ ($1\ensuremath{\sigma}$, statistical) as compared to the expected result of ${b}_{g}\ensuremath{\sim}1.8$ for this sample. We discuss possible instrument-related systematic errors and show that the galactic foregrounds are not important. We do not find any evidence for point-source or thermal Sunyaev-Zel'dovich effect contamination.

Low CMB quadrupole from dark energy isocurvature perturbations

We explicate the origin of the temperature quadrupole in the adiabatic dark energy model and explore the mechanism by which scale invariant isocurvature dark energy perturbations can lead to its sharp suppression. The model requires anticorrelated curvature and isocurvature fluctuations and is favored by the Wilkinson Microwave Anisotropy Probe data at about the 95% confidence level in a flat scale invariant model. In an inflationary context, the anticorrelation may be established if the curvature fluctuations originate from a variable decay rate of the inflaton; such models however tend to overpredict gravitational waves. This isocurvature model can in the future be distinguished from alternatives involving a reduction in large scale power or modifications to the sound speed of the dark energy through the polarization and its cross correlation with the temperature. The isocurvature model retains the same polarization fluctuations as its adiabatic counterpart but reduces the correlated temperature fluctuations. We present a pedagogical discussion of dark energy fluctuations in a quintessence and k-essence context in the Appendix.

Assessing the effects of foregrounds and sky removal in WMAP

Many recent analyses have indicated that large scale Wilkinson Microwave Anisotropy Probe (WMAP) data display anomalies that appear inconsistent with the standard cosmological paradigm. However, the effects of foreground contamination, which require elimination of some fraction of the data, have not been fully investigated due to the complexity in the analysis. Here we develop a general formalism of how to incorporate these effects into any analysis of this type. Our approach is to compute the full multidimensional probability distribution function of all possible sky realizations that are consistent with the data and with the allowed level of contamination. Any statistic can be integrated over this probability distribution to assess its significance. As an example we apply this method to compute the joint probability distribution function for the possible realizations of quadrupole and octopole using the WMAP data. This 12 dimensional distribution function is explored using the Markov Chain Monte Carlo technique. The resulting chains are used to assess the statistical significance of the low quadrupole using frequentist methods, which we find to be 3-4%. Octopole is normal and the probability of it being anomalously low or as low as WMAP reported value is very small. We address the quadrupole-octopole alignmentmore » using several methods that have been recently used to argue for anomalies, such as angular momentum dispersion, multipole vectors and a new method based on feature matching. While we confirm that the full-sky map Internal Linear Combination Map (ILC) suggest an alignment, we find that removing the most contaminated part of the data also removes any evidence of alignment: the probability distributions strongly disfavor the alignment. This suggests that most of the evidence for it comes from non-Gaussian features in the part of the data most contaminated by the foregrounds. We also present an example, that of octopole alignment with the ecliptic, where the statistical significance can be enhanced by removing the contamination.« less

Lorentz-boosted circles-in-the-sky and cosmic topology

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.

Constraining Born-Infeld models of dark energy with CMB anisotropies

We study the cosmic microwave background (CMB) anisotropies constraints on two Dark Energy models described by scalar fields with different Lagrangians, namely, a Klein-Gordon and a Born-Infeld field. The speed of sound of field fluctuations are different in these two theories, and therefore the predictions for CMB and structure formation are different. Employing the Wilkinson Microwave Anisotropy Probe data on CMB, we make a likelihood analysis on a grid of theoretical models. We constrain the parameters of the models and compute the probability distribution functions for the equation of state. We show that the effect of the different sound speeds affects the low multipoles of CMB anisotropies, but is at most marginal for the class of models studied here.

Sunyaev-Zeldovich effect in WMAP and its effect on cosmological parameters

We use multifrequency information in first year Wilkinson microwave anisotropy probe (WMAP) data to search for the Sunyaev-Zeldovich (SZ) effect. WMAP has sufficiently broad frequency coverage to constrain the SZ effect without the addition of higher frequency data: the SZ power spectrum amplitude is expected to increase 50% from W to Q frequency band. This, in combination with the low noise in WMAP, allows us to strongly constrain the SZ contribution. We derive an optimal frequency combination of WMAP cross-spectra to extract the SZ effect in the presence of noise, cosmic microwave background (CMB), and radio point sources, which are marginalized over. We find that the SZ contribution is less than 2% (95% C.L.) at the first acoustic peak in W band. Under the assumption that the removed radio point sources are not correlated with the SZ effect this limit implies ${\ensuremath{\sigma}}_{8}&lt;1.07$ at 95% C.L. We investigate the effect on the cosmological parameters of allowing an SZ component. We run Monte Carlo Markov chains with and without an SZ component and find that the addition of the SZ effect does not affect any of the cosmological conclusions. We conclude that the SZ effect does not contaminate the WMAP CMB or change cosmological parameters, refuting the recent claims that they may be corrupted.

On Foreground Removal from theWilkinson Microwave Anisotropy ProbeData by an Internal Linear Combination Method: Limitations and Implications

We study the Internal Linear Combination (ILC) method presented by the Wilkinson Microwave Anisotropy Probe (WMAP) science team, with the goal of determining whether it may be used for cosmological purposes, as a template-free alternative to existing foreground-correction methods. We conclude that the method does have the potential to do just that, but great care must be taken both in implementation and in a detailed understanding of limitations caused by residual foregrounds, which can still affect cosmological results. As a first step we demonstrate how to compute the ILC weights both accurately and efficiently by means of Lagrange multipliers, and we apply this method to the observed data to produce a new version of the ILC map. This map has 12% lower variance than the ILC map of the WMAP team, primarily because of less noise. Next we describe how to generate Monte Carlo simulations of the ILC map and find that these agree well with the observed map on angular scales up to l ≈ 200, using a conservative sky cut. Finally we make two comments to the ongoing debates concerning the large-scale properties of the WMAP data. First, we note that the Galactic southeastern quadrant is associated with notably different ILC weights than the other three quadrants, possibly indicating a foreground-related anisotropy. Second, we study the properties of the quadrupole and octopole (amplitude, alignment, and planarity) and reproduce the previously reported results that the quadrupole and octopole are strongly aligned and that the octopole is moderately planar. Even more interestingly, we find that the l = 5 mode is spherically symmetric at about 3 σ, and that the l = 6 mode is planar at the 2 σ level. However, we also assess the impact of residual foregrounds on these statistics, and find that the ILC map is not clean enough to allow for cosmological conclusions. Alternative methods must be developed to study these issues further.

The Effect of Hot Gas in the First-Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Data

By cross-correlating templates constructed from the Two Micron All Sky Survey Extended Source Catalog with the first-year data from the Wilkinson Microwave Anisotropy Probe (WMAP), we search for the thermal Sunyaev-Zel'dovich (tSZ) signature induced by hot gas in the local universe. Assuming that galaxies trace the distribution of hot gas, we select regions on the sky with the largest projected density of galaxies. Under conservative assumptions on the amplitude of foreground residuals, we find a temperature decrement of -35 ± 7 μK (~5 σ detection level, the highest reported so far) in the ~26 deg2 of the sky containing the largest number of galaxies per solid angle. We show that most of the reported signal is caused by known galaxy clusters that, when convolved with the average beam of the WMAP W-band channel, subtend a typical angular size of 20'-30'. Finally, after removing from our analyses all pixels associated with known optical and X-ray galaxy clusters, we still find a tSZ decrement of -96 ± 37 μK in pixels subtending about ~0.8 deg2 on the sky. Most of this signal is coming from five different cluster candidates in the Zone of Avoidance (ZoA), present in the Clusters in the ZoA catalog. We found no evidence that structures less bound than clusters contribute to the tSZ signal present in the WMAP data.

Testing for Non‐Gaussianity in theWilkinson Microwave Anisotropy ProbeData: Minkowski Functionals and the Length of the Skeleton

The three Minkowski functionals and the recently defined length of the skeleton are estimated for the co-added first-year Wilkinson Microwave Anisotropy Probe (WMAP) data and compared with 5000 Monte Carlo simulations, based on Gaussian fluctuations with the a-priori best-fit running-index power spectrum and WMAP-like beam and noise properties. Several power spectrum-dependent quantities, such as the number of stationary points, the total length of the skeleton, and a spectral parameter, gamma, are also estimated. While the area and length Minkowski functionals and the length of the skeleton show no evidence for departures from the Gaussian hypothesis, the northern hemisphere genus has a chi^2 that is large at the 95% level for all scales. For the particular smoothing scale of 3.40 degrees FWHM it is larger than that found in 99.5% of the simulations. In addition, the WMAP genus for negative thresholds in the northern hemisphere has an amplitude that is larger than in the simulations with a significance of more than 3 sigma. On the smallest angular scales considered, the number of extrema in the WMAP data is high at the 3 sigma level. However, this can probably be attributed to the effect of point sources. Finally, the spectral parameter gamma is high at the 99% level in the northern Galactic hemisphere, while perfectly acceptable in the southern hemisphere. The results provide strong evidence for the presence of both non-Gaussian behavior and an unexpected power asymmetry between the northern and southern hemispheres in the WMAP data.

High-sensitivity measurements of the cosmic microwave background power spectrum with the extended Very Small Array

We present deep Ka-band (ν ≈ 33 GHz) observations of the cosmic microwave background (CMB) made with the extended Very Small Array (VSA). This configuration produces a naturally weighted synthesized FWHM beamwidth of ∼11 arcmin, which covers anrange of 300 to 1500. On these scales, foreground extragalactic sources can be a major source of contamination to the CMB anisotropy. This problem has been alleviated by identifying sources at 15 GHz with the Ryle Telescope and then monitoring these sources at 33 GHz using a single-baseline interferometer collocated with the VSA. Sources with flux densities20 mJy at 33 GHz are subtracted from the data. In addition, we calculate a statistical correction for the small residual contribution from weaker sources that are below the detection limit of the survey. The CMB power spectrum corrected for Galactic foregrounds and extragalactic point sources is presented. A totalrange of 150-1500 is achieved by combining the complete extended array data with earlier VSA data in a compact configuration. Our resolution of �� ≈ 60 allows the first three acoustic peaks to be clearly delineated. This is achieved by using mosaiced observations in seven regions covering a total area of 82 deg 2 . There is good agreement with the Wilkinson Microwave Anisotropy Probe (WMAP) data up to � = 700 where WMAP data run out of resolution. For highervalues out to � = 1500, the agreement in power spectrum amplitudes with other experiments is also very good despite differences in frequency and observing technique.

Microwave Interstellar Medium Emission in the Green Bank Galactic Plane Survey: Evidence for Spinning Dust

We observe significant dust-correlated emission outside of H II regions in the Green Bank Galactic Plane Survey (-4? < b < 4?) at 8.35 and 14.35?GHz. The rising spectral slope rules out synchrotron and free-free emission as majority constituents at 14 GHz, and the amplitude is at least 500 times higher than expected thermal dust emission. When combined with the Rhodes (2.326 GHz) and Wilkinson Microwave Anisotropy Probe (23-94 GHz) data, it is possible to fit dust-correlated emission at 2.3-94 GHz with only soft synchrotron, free-free, thermal dust, and an additional dust-correlated component similar to Draine & Lazarian spinning dust. The rising component generally dominates free-free and synchrotron for ? 14?GHz and is overwhelmed by thermal dust at ? 60?GHz. The current data fulfill most of the criteria laid out by Finkbeiner and coworkers for detection of spinning dust.

Confrontation of Modified Newtonian Dynamics Predictions withWilkinson Microwave Anisotropy ProbeFirst Year Data

I present a model devoid of nonbaryonic cold dark matter (CDM) that provides an acceptable fit to the Wilkinson Microwave Anisotropy Probe (WMAP) data for the power spectrum of temperature fluctuations in the cosmic background radiation. An a priori prediction of such no-CDM models was a first-to-second peak amplitude ratio A1:2 � 2:4. WMAP measures A1:2 ¼ 2:34 � 0:09. The baryon content is the dominant factor in fixing this ratio; noCDM models that are consistent with the WMAP data are also consistent with constraints on the baryon density from the primordial abundances of 2 H, 4 He, and 7 Li. However, in order to match the modest width of the acoustic peaks observed by WMAP, a substantial neutrino mass is implied: m� � 1 eV. Even with such a heavy neutrino, structure is expected to form rapidly under the influence of modified Newtonian dynamics. Consequently, the

Cross-correlation studies with CMB polarization maps

The free-electron population during the reionized epoch rescatters the cosmic microwave background (CMB) temperature quadrupole and generates a now well-known polarization signal at large angular scales. While this contribution has been detected in the temperature-polarization cross power spectrum measured with Wilkinson Microwave Anisotropy Probe data, due to the large cosmic variance associated with anisotropy measurements at angular scales of tens of degrees only limited information related to reionization, such as the optical depth to electron scattering, can be extracted. The inhomogeneities in the free-electron population lead to an additional secondary polarization anisotropy contribution at arcminute scales. While the fluctuation amplitude, relative to dominant primordial fluctuations, is small, we suggest that a cross correlation between the arcminute scale CMB polarization data and a tracer field of the high redshift universe, such as through fluctuations captured by the 21 cm neutral hydrogen background or those in the infrared background related to the first protogalaxies, may allow one to study additional details related to reionization. For this purpose, we discuss an optimized higher order correlation measurement, in the form of a three-point function, including information from large angular scale CMB temperature anisotropies in addition to the arcminute scale polarization signal related to inhomogeneous reionization. We suggest that the proposed bispectrum can be measured with a substantial signal-to-noise ratio and does not require all-sky maps of CMB polarization or that of the tracer field. A measurement such as the one proposed may allow one to establish the epoch when CMB polarization related to reionization is generated and to address the question whether the universe was reionized once or twice.

Constraints on alternative models to dark energy

Recent observations of type Ia supernovae strongly support that the universe is accelerating now and decelerated in the recent past. This may be evidence of the breakdown of the standard Friedmann equation. We consider a general modified Friedmann equation. Three different models are analysed in detail. The current supernova data and the Wilkinson microwave anisotropy probe data are used to constrain these models. A detailed analysis of the transition from the deceleration to acceleration phase is also performed.

A Search for Lensing of CMB in Correlation with Large-Scale Structure

We present the results of a search for gravitational lensing of the cosmic microwave background (CMB) in cross-correlation with the projected density of luminous red galaxies (LRGs). The CMB lensing reconstruction is performed using the first year of Wilkinson Microwave Anisotropy Probe (WMAP) data, and the galaxy maps are obtained using the Sloan Digital Sky Survey (SDSS) imaging data. We find no detection of lensing; our constraint on the galaxy bias derived from the galaxy-convergence cross-spectrum is for this sample. We discuss possible instrument-related systematic errors and show that the Galactic foregrounds are not important. We do not find any evidence for point source or thermal Sunyaev-Zel'dovich effect contamination.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A polarized synchrotron template for cosmic microwave background polarization experiments based on 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.