We search for the signature of parity-violating physics in the cosmic microwave background, called cosmic birefringence, using the Planck data release 4. We initially find a birefringence angle of ...β=0.30°±0.11° (68% C.L.) for nearly full-sky data. The values of β decrease as we enlarge the Galactic mask, which can be interpreted as the effect of polarized foreground emission. Two independent ways to model this effect are used to mitigate the systematic impact on β for different sky fractions. We choose not to assign cosmological significance to the measured value of β until we improve our knowledge of the foreground polarization.
The cosmic microwave background (CMB) radiation data obtained by different experiments contain, besides the desired signal, a superposition of microwave sky contributions. Using a wavelet ...decomposition on the sphere, we present a fast and robust method to recover the CMB signal from microwave maps. We present an application to the Wilkinson Microwave Anisotropy Probe (WMAP) polarization data, which shows its good performance, particularly in very polluted regions of the sky. The applied wavelet has the advantages that it requires little computational time in its calculations, it is adapted to the healpix pixelization scheme and it offers the possibility of multiresolution analysis. The decomposition is implemented as part of a fully internal template fitting method, minimizing the variance of the resulting map at each scale. Using a χ2 characterization of the noise, we find that the residuals of the cleaned maps are compatible with those expected from the instrumental noise. The maps are also comparable to those obtained from the WMAP team, but in our case we do not make use of external data sets. In addition, at low resolution, our cleaned maps present a lower level of noise. The E-mode power spectrum
is computed at high and low resolutions, and a cross-power spectrum
is also calculated from the foreground reduced maps of temperature given by WMAP and our cleaned maps of polarization at high resolution. These spectra are consistent with the power spectra supplied by the WMAP team. We detect the E-mode acoustic peak at ℓ∼ 400, as predicted by the standard ΛCDM model. The B-mode power spectrum
is compatible with zero.
Several statistical anomalies in the cosmic microwave background (CMB) temperature anisotropies seem to defy the assumption of a homogeneous and isotropic universe. In particular, a dipole modulation ...has been detected both in WMAP and Planck data. We adapt the methodology proposed by Eriksen et al. on CMB data to galaxy surveys, tracing the large-scale structure. We analyse the National Radio Astronomy Observatory (NRAO) and Very Large Array (VLA) Sky Survey data at a resolution of ∼2° for three different flux thresholds: 2.5, 5.0 and 10.0 mJy, respectively. No evidence of a dipole modulation is found. This result suggests that the origin of the dipole asymmetry found in the CMB cannot be assigned to secondary anisotropies produced at redshifts around z = 1. However, it could still have been generated at redshifts higher or lower, such as the integrated Sachs–Wolfe effect produced by the local structures. Other all-sky surveys, like the infrared WISE catalogue, could help to explore with a high sensitivity a redshift interval closer than the one probed with NVSS.
The non-Gaussian cold spot in the 1-yr Wilkinson Microwave Anisotropy Probe (WMAP) data, described by Vielva et al. and Cruz et al., is analysed in detail in the present paper. First of all, we ...perform a more rigorous calculation of the significance of the non-zero kurtosis detected in WMAP maps by Vielva et al. in wavelet space, mainly generated by the Spot. We confirm the robustness of that detection, since the probability of obtaining this deviation by chance is 0.69 per cent. Afterwards, the morphology of the Spot is studied by applying Spherical Mexican Hat Wavelets with different ellipticities. The shape of the Spot is found to be almost circular. Finally, we discuss if the observed non-Gaussianity in wavelet space can arise from bad subtracted foreground residues in the WMAP maps. We show that the flat frequency dependence of the Spot cannot be explained by a thermal Sunyaev–Zeldovich effect. Based on our present knowledge of Galactic foreground emissions, we conclude that the significance of our detection is not affected by Galactic residues in the region of the Spot. Considering different Galactic foreground estimates, the probability of finding such a big cold spot in Gaussian simulations is always below 1 per cent.
On the void explanation of the Cold Spot Marcos-Caballero, A; Fernández-Cobos, R; Martínez-González, E ...
Monthly notices of the Royal Astronomical Society. Letters,
07/2016, Letnik:
460, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The integrated Sachs–Wolfe (ISW) contribution induced on the cosmic microwave background by the presence of a supervoid as the one detected by Szapudi et al. (2015) is reviewed in this letter in ...order to check whether it could explain the Cold Spot (CS) anomaly. Two different models, previously used for the same purpose, are considered to describe the matter density profile of the void: a top hat function and a compensated profile produced by a Gaussian potential. The analysis shows that, even enabling ellipticity changes or different values for the dark-energy equation of state parameter ω, the ISW contribution due to the presence of the void does not reproduce the properties of the CS.
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