Cross-correlation of the CMB and radio galaxies in real, harmonic and wavelet spaces: detection of the integrated Sachs-Wolfe effect and dark energy constraints

We report the first detection of the ISW effect in wavelet space, at scales in the sky around 7 degrees with a significance of around 3.3 sigma, by cross-correlating the WMAP first-year data and the NRAO VLA Sky Survey (NVSS). In addition, we present a detailed comparison among the capabilities of three different techniques for two different objectives: to detect the ISW and to put constraints in the nature of the dark energy. The three studied techniques are: the cross-angular power spectrum (CAPS, harmonic space), the correlation function (CCF, real space) and the covariance of the Spherical Mexican Hat Wavelet (SMHW) coefficients (CSMHW, wavelet space). We prove that the CSMHW is expected to provide a higher detection of the ISW effect for a certain scale. This prediction has been corroborated by the analysis of the data. The SMHW analysis shows that the cross-correlation signal is caused neither by systematic effects nor foreground contamination. However, by taking into account the information encoded in all the multipoles/scales/angles, the CAPS provides slightly better constraints than the SMHW in the cosmological parameters that define the nature of the dark energy. The limits provided by the CCF are wider than for the other two methods. Two different cases have been studied: 1) a flat Lambda-CDM universe and 2) a flat universe with an equation of state parameter different from -1. In the first case, the CAPS provides (for a bias value of b = 1.6) 0.59 < Lambda density < 0.84 (at 1 sigma CL). Moreover, the CAPS rejects the range Lambda density < 0.1 at 3.5 sigma, which is the highest detection of the dark energy reported up to date. In the second case, the CAPS gives 0.50 < dark energy density < 0.82 and -1.16 < w < 0.43 (at 1 sigma CL).Comment: 12 pages, 7 figures, accepted for publication in MNRAS. Analysis redone. Changes in the estimation of the cosmological parametres. Additional comparison between wavelets and more standard technique

Error analysis in cross-correlation of sky maps: application to the ISW detection

Constraining cosmological parameters from measurements of the Integrated Sachs-Wolfe effect requires developing robust and accurate methods for computing statistical errors in the cross-correlation between maps. This paper presents a detailed comparison of such error estimation applied to the case of cross-correlation of Cosmic Microwave Background (CMB) and large-scale structure data. We compare theoretical models for error estimation with montecarlo simulations where both the galaxy and the CMB maps vary around a fiducial auto-correlation and cross-correlation model which agrees well with the current concordance LCDM cosmology. Our analysis compares estimators both in harmonic and configuration (or real) space, quantifies the accuracy of the error analysis and discuss the impact of partial sky survey area and the choice of input fiducial model on dark-energy constraints. We show that purely analytic approaches yield accurate errors even in surveys that cover only 10% of the sky and that parameter constraints strongly depend on the fiducial model employed. Alternatively, we discuss the advantages and limitations of error estimators that can be directly applied to data. In particular, we show that errors and covariances from the Jack-Knife method agree well with the theoretical approaches and simulations. We also introduce a novel method in real space that is computationally efficient and can be applied to real data and realistic survey geometries. Finally, we present a number of new findings and prescriptions that can be useful for analysis of real data and forecasts, and present a critical summary of the analyses done to date.Comment: submitted to MNRAS, 26 page

Detection of the ISW effect and corresponding dark energy constraints made with directional spherical wavelets

Using a directional spherical wavelet analysis we detect the integrated Sachs-Wolfe (ISW) effect, indicated by a positive correlation between the first-year Wilkinson Microwave Anisotropy Probe (WMAP) and NRAO VLA Sky Survey (NVSS) data. Detections are made using both a directional extension of the spherical Mexican hat wavelet and the spherical butterfly wavelet. We examine the possibility of foreground contamination and systematics in the WMAP data and conclude that these factors are not responsible for the signal that we detect. The wavelet analysis inherently enables us to localise on the sky those regions that contribute most strongly to the correlation. On removing these localised regions the correlation that we detect is reduced in significance, as expected, but it is not eliminated, suggesting that these regions are not the sole source of correlation between the data. This finding is consistent with predictions made using the ISW effect, where one would expect weak correlations over the entire sky. In a flat universe the detection of the ISW effect provides direct and independent evidence for dark energy. We use our detection to constrain dark energy parameters by deriving a theoretical prediction for the directional wavelet covariance statistic for a given cosmological model. Comparing these predictions with the data we place constraints on the equation-of-state parameter $w$ and the vacuum energy density $\Omega_\Lambda$. We also consider the case of a pure cosmological constant, i.e. $w=-1$. For this case we rule out a zero cosmological constant at greater than the 99.9% significance level. All parameter estimates that we obtain are consistent with the standand cosmological concordance model values.Comment: 16 pages, 13 figures; replaced to match version accepted by MNRA

The three-point correlation function of cosmic shear. II: Relation to the bispectrum of the projected mass density and generalized third-order aperture measures

We study the relation of the three-point cosmic shear statistics to the third-order statistical properties of the underlying convergence, expressed in terms of its bispectrum. Explicit relations for the natural components of the shear three-point correlation function in terms of the bispectrum are derived. The behavior of the correlation function under parity transformation is obtained and found to agree with previous results. We find that in contrast to the two-point shear correlation function, the three-point function at a given angular scale \theta is not affected by power in the bispectrum on much larger scales. These relations are then inverted to obtain the bispectrum in terms of the three-point shear correlator; two different expressions, corresponding to different natural components of the shear correlator, are obtained and can be used to separate E and B-mode shear contributions. These relations allow us to explicitly show that correlations containing an odd power of B-mode shear vanish for parity-symmetric fields. Generalizing a recent result by Jarvis et al., we derive expressions for the third-order aperture measures, employing multiple angular scales, in terms of the (natural components of the) three-point shear correlator and show that they contain essentially all the information about the underlying bispectrum. We discuss the many useful features these (generalized) aperture measures have that makes them convenient for future analyses of the skewness of the cosmic shear field (and any other polar field, such as the polarization of the Cosmic Microwave Background). (Abridged)Comment: 18 pages, 3 figures, minor changes made, one paragraph and two figures added. Matches the published versio

Cross-correlation of WMAP 3rd year and the SDSS DR4 galaxy survey: new evidence for Dark Energy

We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR4 (SDSS4) covering 13% of the sky, increasing by a factor of 3.7 the volume sampled in previous analyses. The new measurements confirm a positive cross-correlation with higher significance (total signal-to-noise of about 4.7). The correlation as a function of angular scale is well fitted by the integrated Sachs-Wolfe (ISW) effect for LCDM flat FRW models with a cosmological constant. The combined analysis of different samples gives Omega_L=0.80-0.85$(68$0.77-0.86$ (95% CL). We find similar best fit values for Omega_L for different galaxy samples with median redshifts of z ~0.3 and z ~0.5, indicating that the data scale with redshift as predicted by the LCDM cosmology (with equation of state parameter w=-1). This agreement is not trivial, but can not yet be used to break the degeneracy constraints in the w versus Omega_L plane using only the ISW data.Comment: 5 pages, final version to be published by MNRAS Let. Minor changes with some additional clarification on error analysis don

The Large-Scale Structure of the X-ray Background and its Cosmological Implications

A careful analysis of the HEAO1 A2 2-10 keV full-sky map of the X-ray background (XRB) reveals clustering on the scale of several degrees. After removing the contribution due to beam smearing, the intrinsic clustering of the background is found to be consistent with an auto-correlation function of the form (3.6 +- 0.9) x 10^{-4} theta^{-1} where theta is measured in degrees. If current AGN models of the hard XRB are reasonable and the cosmological constant-cold dark matter cosmology is correct, this clustering implies an X-ray bias factor of b_X ~ 2. Combined with the absence of a correlation between the XRB and the cosmic microwave background, this clustering can be used to limit the presence of an integrated Sachs-Wolfe (ISW) effect and thereby to constrain the value of the cosmological constant, Omega_Lambda < 0.60 (95 % C.L.). This constraint is inconsistent with much of the parameter space currently favored by other observations. Finally, we marginally detect the dipole moment of the diffuse XRB and find it to be consistent with the dipole due to our motion with respect to the mean rest frame of the XRB. The limit on the amplitude of any intrinsic dipole is delta I / I < 5 x 10^{-3} at the 95 % C.L. When compared to the local bulk velocity, this limit implies a constraint on the matter density of the universe of Omega_m^{0.6}/b_X(0) > 0.24.Comment: 15 pages, 8 postscript figures, to appear in the Astrophysical Journal. The postscript version appears not to print, so use the PDF versio

Galactic periodicity and the oscillating G model

We consider the model involving the oscillation of the effective gravitational constant that has been put forward in an attempt to reconcile the observed periodicity in the galaxy number distribution with the standard cosmological models. This model involves a highly nonlinear dynamics which we analyze numerically. We carry out a detailed study of the bound that nucleosynthesis imposes on this model. The analysis shows that for any assumed value for $\Omega$ (the total energy density) one can fix the value of $\Omega_{\rm bar}$ (the baryonic energy density) in such a way as to accommodate the observational constraints coming from the $^4{\rm He}$ primordial abundance. In particular, if we impose the inflationary value $\Omega=1$ the resulting baryonic energy density turns out to be $\Omega_{\rm bar}\sim 0.021$. This result lies in the very narrow range $0.016 \leq \Omega_{\rm bar} \leq 0.026$ allowed by the observed values of the primordial abundances of the other light elements. The remaining fraction of $\Omega$ corresponds to dark matter represented by a scalar field.Comment: Latex file 29 pages with no figures. Please contact M.Salgado for figures. A more careful study of the model appears in gr-qc/960603

Measurement of Electron Trapping in the CESR Storage Ring

The buildup of low-energy electrons has been shown to affect the performance of a wide variety of particle accelerators. Of particular concern is the persistence of the cloud between beam bunch passages, which can impose limitations on the stability of operation at high beam current. We have obtained measurements of long-lived electron clouds trapped in the field of a quadrupole magnet in a positron storage ring, with lifetimes much longer than the revolution period. Based on modeling, we estimate that about 7% of the electrons in the cloud generated by a 20-bunch train of 5.3 GeV positrons with 16-ns spacing and $1.3x10^{11}$ population survive longer than 2.3 $\mu$s in a quadrupole field of gradient 7.4 T/m. We have observed a non-monotonic dependence of the trapping effect on the bunch spacing. The effect of a witness bunch on the measured signal provides direct evidence for the existence of trapped electrons. The witness bunch is also observed to clear the cloud, demonstrating its effectiveness as a mitigation technique.Comment: 6 pages, 9 figures, 28 citation

Attachment forerunners, dyadic sensitivity and development of the child in families with a preterm born baby

Objective: The aim of this study is to explore attachment forerunners and dyadic sensitivity in the family with preterm born child. Methods: 89 families, 35 with preterm born children ( 2500 gr.) were studied from 3 months to 1 year corrected age (267 total subjects). Mother-child and father-child couples were subjected to CARE-Index and both parents to DAS, CES-D and STAI Y-2. The child\u2019s psychomotor development was assessed by Bayley Scales. Results: The mothers of preterm children presented high risk interactive behaviors at CARE-Index (low scores at Dyadic Sensitivity Scale, p = .000), high anxiety (p = .003) and depression (p = .03). Preterm fathers presented low scores at Dyadic Sensitivity Scale (p = .000) and high anxiety (p = .024). In interaction, attachment forerunners suggest an insecure attachment in preterm mothers (p = .001) and fathers (p = .000) and in preterm children in the interaction with the mother (p = .028). These risk factors were correlated, in both parents, with low performance of the child at Bayley Scales (p =.04). Fathers of preterm children presented also a negative perception of the child and an unsatisfied perception of the hospital care. Conclusions: The results show in the preterm family that 40% of mothers and 75% of fathers are in high risk area suggested by CARE-Index. In these cases, insecure attachment forerunners, low dyadic sensitivity and psychological difficulties (couple conflicts, anxiety, depression) seem to influence the psychomotor development of the preterm child