Search

The connection between the dipolar modulation asymmetry and the quadrupole-octopole alignment in the CMB is studied in this work. First, a generalization of the dipolar modulation model is proposed by considering that the amplitude may depend on the scale. As derived from a Bayesian inference analysis, this model fits the CMB data better than the scale-independent one. As an extension of the standard model, the scale-dependent dipolar modulation shows comparable evidence to the standard isotropic model in the large scales (ℓ ≤ 64). The posterior distribution of the parameters of the scale-dependent model suggests that the amplitude of the dipolar modulation is large at the lowest multipoles. This large asymmetry induces a detectable correlation between the quadrupole and the octopole. The significance of the quadrupole-octopole alignment is analyzed under the assumption that the Universe has a scale-dependent dipolar modulation. The three alignment estimators considered in this paper show an increment of 80% in the p-value. {Therefore, it is found that the alignment between the quadrupole and octopole is more likely assuming a scale-dependent dipolar modulation than in the standard model. Within this dipolar modulation scenario, only one of the alignment estimators is still below the 1% probability level.}, AMC would like to thank Universidad de Cantabria for a post-doctoral contract. AMC and EMG acknowledge financial support from Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER, UE), projects ref. ESP2017-83921-C2-1-R and AYA2017-90675-REDC.

arXiv:1701.08552v1, In the present work, we study the largest structures of the CMB temperature measured by Planck in terms of the most prominent peaks on the sky, which, in particular, are located in the southern galactic hemisphere. Besides these large-scale features, the well-known Cold Spot anomaly is included in the analysis. All these peaks would contribute significantly to some of the CMB large-scale anomalies, as the parity and hemispherical asymmetries, the dipole modulation, the alignment between the quadrupole and the octopole, or in the case of the Cold Spot, to the non-Gaussianity of the field. The analysis of the peaks is performed by using their multipolar profiles, which characterize the local shape of the peaks in terms of the discrete Fourier transform of the azimuthal angle. In order to quantify the local anisotropy of the peaks, the distribution of the phases of the multipolar profiles is studied by using the Rayleigh random walk methodology. Finally, a direct analysis of the 2-dimensional field around the peaks is performed in order to take into account the effect of the galactic mask. The results of the analysis conclude that, once the peak amplitude and its first and second order derivatives at the centre are conditioned, the rest of the field is compatible with the standard model. In particular, it is observed that the Cold Spot anomaly is caused by the large value of curvature at the centre., Partial financial support from the Spanish Ministerio de Economía y Competitividad Projects AYA2012-39475-C02-01 and Consolider-Ingenio 2010 CSD2010-00064 is acknowledged.

arXiv:1701.08548v1, We study the Planck CMB temperature at different scales through its derivatives up to second order, which allows one to characterize the local shape and isotropy of the field. The problem of having an incomplete sky in the calculation and statistical characterization of the derivatives is addressed in the paper. The analysis confirms the existence of a low variance in the CMB at large scales, which is also noticeable in the derivatives. Moreover, deviations from the standard model in the gradient, curvature and the eccentricity tensor are studied in terms of extreme values on the data. As it is expected, the Cold Spot is detected as one of the most prominent peaks in terms of curvature, but additionally, when the information of the temperature and its Laplacian are combined, another feature with similar probability at the scale of 10° is also observed. However, the p-value of these two deviations increase above the 6% when they are referred to the variance calculated from the theoretical fiducial model, indicating that these deviations can be associated to the low variance anomaly. Finally, an estimator of the directional anisotropy for spinorial quantities is introduced, which is applied to the spinors derived from the field derivatives. An anisotropic direction whose probability is, Partial financial support from the Spanish Ministerio de Economía y Competitividad Projects AYA2012-39475-C02-01 and Consolider-Ingenio 2010 CSD2010-00064 is acknowledged.

We present a theoretical study of CMB temperature peaks, including its effect over the polarization field, and allowing nonzero eccentricity. The formalism is developed in harmonic space and using the covariant derivative on the sphere, which guarantees that the expressions obtained are completely valid at large scales (i.e., no flat approximation). The expected patterns induced by the peak, either in temperature or polarization, are calculated, as well as their covariances. It is found that the eccentricity introduces a quadrupolar dependence in the peak shape, which is proportional to a complex bias parameter $b_\epsilon$, characterizing the peak asymmetry and orientation. In addition, the one-point statistics of the variables defining the peak on the sphere is reviewed, finding some differences with respect to the flat case for large peaks. Finally, we present a mechanism to simulate constrained CMB maps with a particular peak on the field, which is an interesting tool for analysing the statistical properties of the peaks present in the data.