We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Ba... more We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Background (CMB) delivered by the WMAP experiment in search for a parity violating signal. Such a signal could be seeded by new physics beyond the standard model, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the linear polarization direction of a CMB photon may get rotated during its cosmological journey, a phenomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset the WMAP and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a non zero rotation. By using wavelet transforms we set a tighter limit on the CMB photon rotation angle ∆α = −2.5± 3.0 (∆α = −2.5± 6.0) at the one (two) σ level, consistent with a null detection.
Context. The measured cosmic microwave background (CMB) angular distribution shows high consisten... more Context. The measured cosmic microwave background (CMB) angular distribution shows high consistency with the ΛCDM model, which predicts cosmological isotropy as one of its fundamental characteristics. However, isotropy violations were reported in CMB temperature maps of the Wilkinson Microwave Anisotropy Probe (WMAP) and confirmed by Planck satellite data. Aims. Our purpose is to investigate the influence of different sky cuts (masks) employed in the analysis of CMB angular distribution, in particular in the excess of power in the southeastern quadrant (SEQ) and the lack of power in the northeastern quadrant (NEQ), found in both WMAP and Planck data. Methods. We compared the two-point correlation function (TPCF) computed for each quadrant of the CMB foreground-cleaned temperature maps to 1000 Monte Carlo (MC) simulations generated assuming the ΛCDM best-fit power spectrum using four different masks, from the least to the most severe one: mask-rulerminimal, UT78, U73, and U66. In addition to the quadrants and for a better understanding of these anomalies, we computed the TPCF using the mask-rulerminimal for circular regions in the map where the excess and lack of power are present. We also compared, for completeness, the effect of Galactic cuts (+/−10, 20, 25, and 30 degrees above/below the Galactic plane) in the TPCF calculations as compared to the MC simulations. Results. We found consistent results for three masks, namely mask-rulerminimal, U73, and U66. The results indicate that the excess of power in the SEQ tends to vanish as the portion of the sky covered by the mask increases and the lack of power in the NEQ remains virtually unchanged. A different result arises for the newly released UT78 Planck mask. When this mask is applied, the NEQ is no longer anomalous. On the other hand, the excess of power in the SEQ becomes the most significant one among the masks. Nevertheless, the asymmetry between the SEQ and NEQ is independent of the mask and it disagrees with the isotropic model with at least 95% C.L. Conclusions. We find that UT78 disagrees with the other analyzed masks, especially when considering the SEQ and the NEQ individual analysis. Most important, the use of UT78 washes out the anomaly in the NEQ. Furthermore, we find an excess of kurtosis, compared with simulations, in the NEQ for the regions not masked by UT78 but masked by the other masks, indicating that the previous result could be due to unremoved residual foregrounds by UT78.
Context. Some peculiar features found in the angular distribution of the cosmic microwave backgro... more Context. Some peculiar features found in the angular distribution of the cosmic microwave background (CMB) measured by the Wilkinson Microwave Anisotropy Probe (WMAP) deserve further investigation. Among these peculiar features, is the quadrant asymmetry, which is likely related to the north-south asymmetry. Aims. In this paper, we aim to extend the analysis of the quadrant asymmetry in the ΛCDM framework to the Planck foregroundcleaned maps, using the mask provided by Planck team. Methods. We compute the two-point correlation function (TPCF) from each quadrant of the Planck CMB sky maps, and compare the result with 1000 Monte Carlo (MC) simulations generated assuming the ΛCDM best-fit power spectrum. Results. We detect the presence of an excess of power in the southeastern quadrant (SEQ) and a significant lack of power in the northeastern quadrant (NEQ) in the Planck data. Asymmetries between the SEQ and the other three quadrants (southwestern quadrant (SWQ), northwestern quadrant (NWQ), and NEQ) are each in disagreement with an isotropic sky at a 95% confidence level. Furthermore, by rotating the Planck temperature sky map with respect to z direction, we showed the rotation angle where the TPCF of the SEQ has its maximal power. Conclusions. Our analysis of the Planck foreground-cleaned maps shows that there is an excess of power in the TPCF in the SEQ and a significant lack of power in the NEQ when compared with simulations. This asymmetry is anomalous when considering the ΛCDM framework .
We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Ba... more We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Background (CMB) delivered by the WMAP experiment in search for a parity violating signal. Such a signal could be seeded by new physics beyond the standard model, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the linear polarization direction of a CMB photon may get rotated during its cosmological journey, a phenomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset the WMAP and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a non zero rotation. By using wavelet transforms we set a tighter limit on the CMB photon rotation angle ∆α = −2.5 ± 3.0 (∆α = −2.5 ± 6.0) at the one (two) σ level, consistent with a null detection.
We report measurements of the CMB polarization power spectra from the January 2003 Antarctic flig... more We report measurements of the CMB polarization power spectra from the January 2003 Antarctic flight of Boomerang. The primary results come from six days of observation of a patch covering 0.22% of the sky centered near R.A. = 82.5 • , Dec = −45 •. The observations were made using four pairs of polarization sensitive bolometers operating in bands centered at 145 GHz. Using two independent analysis pipelines, we measure a non-zero EE signal in the range 100 < ℓ < 1000 with a significance 4.8σ, a 2σ upper limit of 8.6 µK 2 for any BB contribution, and a 2σ upper limit of 7.0 µK 2 for the EB spectrum. Estimates of foreground intensity fluctuations and the non-detection of BB and EB signals rule out any significant contribution from galactic foregrounds. The results are consistent with a ΛCDM cosmology seeded by adiabatic perturbations. We note that this is the first detection of CMB polarization with bolometric detectors.
Using the five-year WMAP data, we re-investigate claims of non-Gaussianities and asymmetries dete... more Using the five-year WMAP data, we re-investigate claims of non-Gaussianities and asymmetries detected in local curvature statistics of the one-year WMAP data. In Hansen et al., it was found that the northern ecliptic hemisphere was non-Gaussian at the ∼1% level testing the densities of hill, lake, and saddle points based on the second derivatives of the cosmic microwave background temperature map. The five-year WMAP data have a much lower noise level and better control of systematics. Using these, we find that the anomalies are still present at a consistent level. Also the direction of maximum non-Gaussianity remains. Due to limited availability of computer resources, Hansen et al. were unable to calculate the full covariance matrix for the χ2-test used. Here, we apply the full covariance matrix instead of the diagonal approximation and find that the non-Gaussianities disappear and there is no preferred non-Gaussian direction. We compare with simulations of weak lensing to see if th...
We investigate local variations of the primordial non-Gaussianity parameter f NL in the WMAP data... more We investigate local variations of the primordial non-Gaussianity parameter f NL in the WMAP data, looking for possible influence of foreground contamination in the full-sky estimate of f NL. We first improve the needlet bispectrum estimate in Rudjord et al. on the full sky to f NL = 73 ± 31 using the KQ75 mask on the co-added V + W channel. We find no particular values of f NL estimates close to the galactic plane and conclude that foregrounds are unlikely to affect the estimate of f NL in the V and W bands even for the smaller KQ85 mask. In the Q band, however, we find unexpectedly high values of f NL in local estimates close to the galactic mask, as well as significant discrepancies between Q-band estimates and V/W-band estimates. We therefore conclude that the Q band is too contaminated to be used for non-Gaussianity studies even with the larger KQ75 mask. We further note that the local f NL estimates on the V + W channel are positive on all equatorial bands from the north to the south pole. The probability for this to happen in a universe with f NL = 0 is less than 1%.
We introduce NeedATool (Needlet Analysis Tool), a software for data analysis based on needlets, a... more We introduce NeedATool (Needlet Analysis Tool), a software for data analysis based on needlets, a wavelet rendition which is powerful for the analysis of fields defined on a sphere. Needlets have been applied successfully to the treatment of astrophysical and cosmological observations, and in particular to the analysis of cosmic microwave background (CMB) data. Usually, such analyses are performed in real space as well as in its dual domain, the harmonic one. Both spaces have advantages and disadvantages: for example, in pixel space it is easier to deal with partial sky coverage and experimental noise; in harmonic domain, beam treatment and comparison with theoretical predictions are more effective. During the last decade, however, wavelets have emerged as a useful tool for CMB data analysis, since they allow to combine most of the advantages of the two spaces, one of the main reasons being their sharp localisation. In this paper, we outline the analytical properties of needlets and discuss the main features of the numerical code, which should be a valuable addition to the CMB analyst's toolbox.
We report on observations of the cosmic microwave background (CMB) obtained during the 2003 Janua... more We report on observations of the cosmic microwave background (CMB) obtained during the 2003 January flight of BOOMERANG. These results are derived from 195 hr of observation with four 145 GHz polarization-sensitive bolometer (PSB) pairs, identical in design to the four 143 GHz Planck High Frequency Instrument (HFI) polarized pixels. The data include 75 hr of observations distributed over 1.84% of the sky with an additional 120 hr concentrated on the central portion of the field, which represents 0.22% of the full sky. From these data we derive an estimate of the angular power spectrum of temperature fluctuations of the CMB in 24 bands over the multipole range 50 l 1500. A series of features, consistent with those expected from acoustic oscillations in the primordial photonbaryon fluid, are clearly evident in the power spectrum, as is the exponential damping of power on scales smaller than the photon mean free path at the epoch of last scattering (l k 900). As a consistency check, the collaboration has performed two fully independent analyses of the time-ordered data, which are found to be in excellent agreement. Subject headingg s: cosmic microwave background-cosmology: observations-instrumentation: detectors Online material: color figures
We apply spherical needlets to the Wilkinson Microwave Anisotropy Probe 5-year cosmic microwave b... more We apply spherical needlets to the Wilkinson Microwave Anisotropy Probe 5-year cosmic microwave background (CMB) data set, to search for imprints of nonisotropic features in the CMB sky. We use the needlets' localization properties to resolve peculiar features in the CMB sky and to study how these features contribute to the anisotropy power spectrum of the CMB. In addition to the now well-known "cold spot" of the CMB map in the southern hemisphere, we also find two hot spots at greater than 99% confidence level, again in the southern hemisphere and closer to the Galactic plane. While the cold spot contributes to the anisotropy power spectrum in the multipoles between ℓ = 6 to ℓ = 33, the hot spots are found to be dominating the anisotropy power in the range between ℓ = 6 and ℓ = 18. Masking both the cold and the two hot spots results in a reduction by about 15% in the amplitude of the angular power spectrum of CMB around ℓ = 10. The resulting changes to the cosmological parameters when the power spectrum is estimated masking these features (in addition to the WMAP team's KQ85 mask) are within the 1σ errors published with the WMAP mask only. We also study the asymmetry between the angular power spectra evaluated on the northern and southern hemispheres. When the features detected by needlets are masked, we find that the difference in the power, measured in terms of the anisotropy variance between ℓ = 4 and ℓ = 18, is reduced by a factor 2. We make available a mask related to needlet features for more detailed studies on asymmetries in the CMB anisotropy sky.
We present a comparison between three approaches to test non-Gaussianity of cosmic microwave back... more We present a comparison between three approaches to test non-Gaussianity of cosmic microwave background data. The Minkowski functionals, the empirical process method and the skewness of wavelet coefficients are applied to maps generated from non-standard inflationary models and to Gaussian maps with point sources included. We discuss the different power of the pixel, harmonic and wavelet space methods on these simulated almost full-sky data (with Planck like noise). We also suggest a new procedure consisting of a combination of statistics in pixel, harmonic and wavelet space.
We analyze the BOOMERanG 2003 (B03) 145 GHz temperature map to constrain the amplitude of a non G... more We analyze the BOOMERanG 2003 (B03) 145 GHz temperature map to constrain the amplitude of a non Gaussian, primordial contribution to CMB fluctuations. We perform a pixel space analysis restricted to a portion of the map chosen in view of high sensitivity, very low foreground contamination and tight control of systematic effects. We set up an estimator based on the three Minkowski functionals which relies on high quality simulated data, including non Gaussian CMB maps. We find good agreement with the Gaussian hypothesis and derive the first limits based on BOOMERanG data for the non linear coupling parameter f NL as −300 < f NL < 650 at 68% CL and −800 < f NL < 1050 at 95% CL.
Monthly Notices of the Royal Astronomical Society: Letters, 2009
We apply the needlet formalism to the Wilkinson Microwave Anisotropy Probe 5-year data, looking f... more We apply the needlet formalism to the Wilkinson Microwave Anisotropy Probe 5-year data, looking for evidence of non-Gaussianity in the bispectrum of the needlet amplitudes. We confirm earlier findings of an asymmetry in the non-Gaussianity between the northern and southern galactic hemispheres. We attempt to isolate which scales and geometrical configurations are most anomalous, and find the bispectrum is most significant on large scales and in the more co-linear configurations, and also in the 'squeezed' configurations. However, these anomalies do not appear to affect the estimate of the non-linear parameter f NL , and we see no significant difference between its value measured in the two hemispheres.
Monthly Notices of the Royal Astronomical Society, 2005
We use the PSCz galaxy redshift catalogue combined with constrained simulations based on the IRAS... more We use the PSCz galaxy redshift catalogue combined with constrained simulations based on the IRAS 1.2 Jy galaxy density field to estimate the contribution of hot gas in the local universe to the SZ-effect on large scales. We produce a full sky Healpix map predicting the SZ-effect from clusters as well as diffuse hot gas within 80 h −1 Mpc. Performing cross-correlation tests between this map and the WMAP data in pixel, harmonic and wavelet space we can put an upper limit on the effect. We conclude that the SZ effect from diffuse gas in the local universe cannot be detected in current CMB data and is not a contaminating factor on large scales (ℓ < 60) in studies of the CMB angular anisotropies. However, for future high sensitivity experiments observing at a wider range of frequencies, the predicted large scale SZ effect could be of importance.
Monthly Notices of the Royal Astronomical Society, 2005
We test the consistency of estimates of the non-linear coupling constant f NL using non-Gaussian ... more We test the consistency of estimates of the non-linear coupling constant f NL using non-Gaussian CMB maps generated by the method described in (Liguori, Matarrese & Moscardini 2003). This procedure to obtain non-Gaussian maps differs significantly from the method used to obtain f NL in previous works. Nevertheless, using spherical wavelets we find results in very good agreement with (Mukherjee & Wang 2004), showing that the two ways of generating primordial non-Gaussian maps give equivalent results. Moreover, we introduce a new method for estimating the non-linear coupling constant from CMB observations by using the local curvature of the temperature fluctuation field. Using this method, we estimate f NL = 30 ± 210 at the 2σ level. We present both Bayesian credible regions (assuming a flat prior) and proper (frequentist) confidence intervals on f NL , and discuss the relation between the two approaches. The two procedures produce markedly different outcomes, proving that a careful analysis on their different interpretations is needed.
Monthly Notices of the Royal Astronomical Society, 2010
We constrain the amplitude of primordial non-Gaussianity in the cosmic microwave background data ... more We constrain the amplitude of primordial non-Gaussianity in the cosmic microwave background data taking into account the presence of foreground residuals in the maps. We generalize the needlet bispectrum estimator marginalizing over the amplitudes of thermal dust, free-free and synchrotron templates. We apply our procedure to Wilkinson Microwave Anisotropy Probe 5-year data, finding f NL = 38 ± 47 (1σ), while the analysis without marginalization provides f NL = 35 ± 42. Splitting the marginalization over each foreground separately, we found that the estimates of f NL are positively cross-correlated of 17 and 12 per cent with the dust and synchrotron, respectively, while a negative cross-correlation of about −10 per cent is found for the free-free component.
Monthly Notices of the Royal Astronomical Society, 2010
We test the asymmetry of the cosmic microwave background anisotropy jointly in temperature and po... more We test the asymmetry of the cosmic microwave background anisotropy jointly in temperature and polarization. We study the hemispherical asymmetry, previously found only in the temperature field, with respect to the axis identified by Hansen et al. To this extent, we make use of the low-resolution Wilkinson Microwave Anisotropy Probe 5-yr temperature and polarization N side = 16 maps and our implementation of an optimal power spectrum estimator. We consider two simple estimators for the power asymmetry and we compare our findings with Monte Carlo simulations which take into account the full noise covariance matrix. We confirm an excess of power in temperature angular power spectrum in the Southern hemisphere at a significant level, between 3σ and 4σ depending on the exact range of multipoles considered. We do not find significant power asymmetry in the gradient (curl) component EE (BB) of polarized angular spectra. Furthermore, cross-correlation power spectra, i.e. TE, TB, EB, show no significant hemispherical asymmetry. We also show that the cold spot found by Vielva et al. in the Southern Galactic hemisphere does not alter the significance of the hemispherical asymmetries on multipoles which can be probed by maps at resolution N side = 16. Although the origin of the hemispherical asymmetry in temperature remains unclear, the study of the polarization pattern could add useful information on its explanation. We therefore forecast by Monte Carlo the Planck capabilities in probing polarization asymmetries.
Monthly Notices of the Royal Astronomical Society, 2010
The parity symmetry of the cosmic microwave background (CMB) pattern as seen by Wilkinson Microwa... more The parity symmetry of the cosmic microwave background (CMB) pattern as seen by Wilkinson Microwave Anisotropy Probe 7 yr (WMAP 7 yr) is tested jointly in temperature and polarization at large angular scale. A quadratic maximum likelihood (QML) estimator is applied to the WMAP 7-yr low-resolution maps to compute all polarized CMB angular power spectra. The analysis is supported by 10 000 realistic Monte Carlo realizations. We confirm the previously reported parity anomaly for TT in the range δ = [2, 22] at >99.5 per cent C.L. No anomalies have been detected in TT for a wider range (up to max = 40). No violations have been found for EE, TE and BB which we test here for the first time. The cross-spectra TB and EB are found to be consistent with zero. We also forecast Planck capabilities in probing parity violations on low-resolution maps.
Monthly Notices of the Royal Astronomical Society, 2006
We propose a fast and efficient bispectrum statistic for cosmic microwave background (CMB) temper... more We propose a fast and efficient bispectrum statistic for cosmic microwave background (CMB) temperature anisotropies to constrain the amplitude of the primordial non-Gaussian signal measured in terms of the non-linear coupling parameter f NL. We show how the method can achieve a remarkable computational advantage by focusing on subsets of the multipole configurations, where the non-Gaussian signal is more concentrated. The detection power of the test increases roughly linearly with the maximum multipole, as shown in the ideal case of an experiment without noise and gaps. The CPU-time scales as 3 max instead of 5 max for the full bispectrum, which for Planck resolution max ∼ 3000 means an improvement in speed of a factor of 10 7 compared with the full bispectrum analysis with minor loss in precision. This approach is complementary to the fast method introduced by Komatsu, Spergel & Wandelt using a reconstruction of the primordial fluctuation field. We find that the introduction of a galactic cut partially destroys the optimality of the configuration, which will then need to be dealt with in the future. We find for an ideal experiment with max = 2000 that upper limits of f NL < 8 can be obtained at 1σ. For the case of the WMAP experiment, we would be able to put limits of | f NL | < 40 if no galactic cut were present. Using the real data with a galactic cut, we obtain an estimate of −80 < f NL < 80 and −160 < f NL < 160 at 1 and 2σ , respectively.
We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Ba... more We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Background (CMB) delivered by the WMAP experiment in search for a parity violating signal. Such a signal could be seeded by new physics beyond the standard model, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the linear polarization direction of a CMB photon may get rotated during its cosmological journey, a phenomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset the WMAP and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a non zero rotation. By using wavelet transforms we set a tighter limit on the CMB photon rotation angle ∆α = −2.5± 3.0 (∆α = −2.5± 6.0) at the one (two) σ level, consistent with a null detection.
Context. The measured cosmic microwave background (CMB) angular distribution shows high consisten... more Context. The measured cosmic microwave background (CMB) angular distribution shows high consistency with the ΛCDM model, which predicts cosmological isotropy as one of its fundamental characteristics. However, isotropy violations were reported in CMB temperature maps of the Wilkinson Microwave Anisotropy Probe (WMAP) and confirmed by Planck satellite data. Aims. Our purpose is to investigate the influence of different sky cuts (masks) employed in the analysis of CMB angular distribution, in particular in the excess of power in the southeastern quadrant (SEQ) and the lack of power in the northeastern quadrant (NEQ), found in both WMAP and Planck data. Methods. We compared the two-point correlation function (TPCF) computed for each quadrant of the CMB foreground-cleaned temperature maps to 1000 Monte Carlo (MC) simulations generated assuming the ΛCDM best-fit power spectrum using four different masks, from the least to the most severe one: mask-rulerminimal, UT78, U73, and U66. In addition to the quadrants and for a better understanding of these anomalies, we computed the TPCF using the mask-rulerminimal for circular regions in the map where the excess and lack of power are present. We also compared, for completeness, the effect of Galactic cuts (+/−10, 20, 25, and 30 degrees above/below the Galactic plane) in the TPCF calculations as compared to the MC simulations. Results. We found consistent results for three masks, namely mask-rulerminimal, U73, and U66. The results indicate that the excess of power in the SEQ tends to vanish as the portion of the sky covered by the mask increases and the lack of power in the NEQ remains virtually unchanged. A different result arises for the newly released UT78 Planck mask. When this mask is applied, the NEQ is no longer anomalous. On the other hand, the excess of power in the SEQ becomes the most significant one among the masks. Nevertheless, the asymmetry between the SEQ and NEQ is independent of the mask and it disagrees with the isotropic model with at least 95% C.L. Conclusions. We find that UT78 disagrees with the other analyzed masks, especially when considering the SEQ and the NEQ individual analysis. Most important, the use of UT78 washes out the anomaly in the NEQ. Furthermore, we find an excess of kurtosis, compared with simulations, in the NEQ for the regions not masked by UT78 but masked by the other masks, indicating that the previous result could be due to unremoved residual foregrounds by UT78.
Context. Some peculiar features found in the angular distribution of the cosmic microwave backgro... more Context. Some peculiar features found in the angular distribution of the cosmic microwave background (CMB) measured by the Wilkinson Microwave Anisotropy Probe (WMAP) deserve further investigation. Among these peculiar features, is the quadrant asymmetry, which is likely related to the north-south asymmetry. Aims. In this paper, we aim to extend the analysis of the quadrant asymmetry in the ΛCDM framework to the Planck foregroundcleaned maps, using the mask provided by Planck team. Methods. We compute the two-point correlation function (TPCF) from each quadrant of the Planck CMB sky maps, and compare the result with 1000 Monte Carlo (MC) simulations generated assuming the ΛCDM best-fit power spectrum. Results. We detect the presence of an excess of power in the southeastern quadrant (SEQ) and a significant lack of power in the northeastern quadrant (NEQ) in the Planck data. Asymmetries between the SEQ and the other three quadrants (southwestern quadrant (SWQ), northwestern quadrant (NWQ), and NEQ) are each in disagreement with an isotropic sky at a 95% confidence level. Furthermore, by rotating the Planck temperature sky map with respect to z direction, we showed the rotation angle where the TPCF of the SEQ has its maximal power. Conclusions. Our analysis of the Planck foreground-cleaned maps shows that there is an excess of power in the TPCF in the SEQ and a significant lack of power in the NEQ when compared with simulations. This asymmetry is anomalous when considering the ΛCDM framework .
We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Ba... more We perform a wavelet analysis of the temperature and polarization maps of the Cosmic Microwave Background (CMB) delivered by the WMAP experiment in search for a parity violating signal. Such a signal could be seeded by new physics beyond the standard model, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the linear polarization direction of a CMB photon may get rotated during its cosmological journey, a phenomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset the WMAP and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a non zero rotation. By using wavelet transforms we set a tighter limit on the CMB photon rotation angle ∆α = −2.5 ± 3.0 (∆α = −2.5 ± 6.0) at the one (two) σ level, consistent with a null detection.
We report measurements of the CMB polarization power spectra from the January 2003 Antarctic flig... more We report measurements of the CMB polarization power spectra from the January 2003 Antarctic flight of Boomerang. The primary results come from six days of observation of a patch covering 0.22% of the sky centered near R.A. = 82.5 • , Dec = −45 •. The observations were made using four pairs of polarization sensitive bolometers operating in bands centered at 145 GHz. Using two independent analysis pipelines, we measure a non-zero EE signal in the range 100 < ℓ < 1000 with a significance 4.8σ, a 2σ upper limit of 8.6 µK 2 for any BB contribution, and a 2σ upper limit of 7.0 µK 2 for the EB spectrum. Estimates of foreground intensity fluctuations and the non-detection of BB and EB signals rule out any significant contribution from galactic foregrounds. The results are consistent with a ΛCDM cosmology seeded by adiabatic perturbations. We note that this is the first detection of CMB polarization with bolometric detectors.
Using the five-year WMAP data, we re-investigate claims of non-Gaussianities and asymmetries dete... more Using the five-year WMAP data, we re-investigate claims of non-Gaussianities and asymmetries detected in local curvature statistics of the one-year WMAP data. In Hansen et al., it was found that the northern ecliptic hemisphere was non-Gaussian at the ∼1% level testing the densities of hill, lake, and saddle points based on the second derivatives of the cosmic microwave background temperature map. The five-year WMAP data have a much lower noise level and better control of systematics. Using these, we find that the anomalies are still present at a consistent level. Also the direction of maximum non-Gaussianity remains. Due to limited availability of computer resources, Hansen et al. were unable to calculate the full covariance matrix for the χ2-test used. Here, we apply the full covariance matrix instead of the diagonal approximation and find that the non-Gaussianities disappear and there is no preferred non-Gaussian direction. We compare with simulations of weak lensing to see if th...
We investigate local variations of the primordial non-Gaussianity parameter f NL in the WMAP data... more We investigate local variations of the primordial non-Gaussianity parameter f NL in the WMAP data, looking for possible influence of foreground contamination in the full-sky estimate of f NL. We first improve the needlet bispectrum estimate in Rudjord et al. on the full sky to f NL = 73 ± 31 using the KQ75 mask on the co-added V + W channel. We find no particular values of f NL estimates close to the galactic plane and conclude that foregrounds are unlikely to affect the estimate of f NL in the V and W bands even for the smaller KQ85 mask. In the Q band, however, we find unexpectedly high values of f NL in local estimates close to the galactic mask, as well as significant discrepancies between Q-band estimates and V/W-band estimates. We therefore conclude that the Q band is too contaminated to be used for non-Gaussianity studies even with the larger KQ75 mask. We further note that the local f NL estimates on the V + W channel are positive on all equatorial bands from the north to the south pole. The probability for this to happen in a universe with f NL = 0 is less than 1%.
We introduce NeedATool (Needlet Analysis Tool), a software for data analysis based on needlets, a... more We introduce NeedATool (Needlet Analysis Tool), a software for data analysis based on needlets, a wavelet rendition which is powerful for the analysis of fields defined on a sphere. Needlets have been applied successfully to the treatment of astrophysical and cosmological observations, and in particular to the analysis of cosmic microwave background (CMB) data. Usually, such analyses are performed in real space as well as in its dual domain, the harmonic one. Both spaces have advantages and disadvantages: for example, in pixel space it is easier to deal with partial sky coverage and experimental noise; in harmonic domain, beam treatment and comparison with theoretical predictions are more effective. During the last decade, however, wavelets have emerged as a useful tool for CMB data analysis, since they allow to combine most of the advantages of the two spaces, one of the main reasons being their sharp localisation. In this paper, we outline the analytical properties of needlets and discuss the main features of the numerical code, which should be a valuable addition to the CMB analyst's toolbox.
We report on observations of the cosmic microwave background (CMB) obtained during the 2003 Janua... more We report on observations of the cosmic microwave background (CMB) obtained during the 2003 January flight of BOOMERANG. These results are derived from 195 hr of observation with four 145 GHz polarization-sensitive bolometer (PSB) pairs, identical in design to the four 143 GHz Planck High Frequency Instrument (HFI) polarized pixels. The data include 75 hr of observations distributed over 1.84% of the sky with an additional 120 hr concentrated on the central portion of the field, which represents 0.22% of the full sky. From these data we derive an estimate of the angular power spectrum of temperature fluctuations of the CMB in 24 bands over the multipole range 50 l 1500. A series of features, consistent with those expected from acoustic oscillations in the primordial photonbaryon fluid, are clearly evident in the power spectrum, as is the exponential damping of power on scales smaller than the photon mean free path at the epoch of last scattering (l k 900). As a consistency check, the collaboration has performed two fully independent analyses of the time-ordered data, which are found to be in excellent agreement. Subject headingg s: cosmic microwave background-cosmology: observations-instrumentation: detectors Online material: color figures
We apply spherical needlets to the Wilkinson Microwave Anisotropy Probe 5-year cosmic microwave b... more We apply spherical needlets to the Wilkinson Microwave Anisotropy Probe 5-year cosmic microwave background (CMB) data set, to search for imprints of nonisotropic features in the CMB sky. We use the needlets' localization properties to resolve peculiar features in the CMB sky and to study how these features contribute to the anisotropy power spectrum of the CMB. In addition to the now well-known "cold spot" of the CMB map in the southern hemisphere, we also find two hot spots at greater than 99% confidence level, again in the southern hemisphere and closer to the Galactic plane. While the cold spot contributes to the anisotropy power spectrum in the multipoles between ℓ = 6 to ℓ = 33, the hot spots are found to be dominating the anisotropy power in the range between ℓ = 6 and ℓ = 18. Masking both the cold and the two hot spots results in a reduction by about 15% in the amplitude of the angular power spectrum of CMB around ℓ = 10. The resulting changes to the cosmological parameters when the power spectrum is estimated masking these features (in addition to the WMAP team's KQ85 mask) are within the 1σ errors published with the WMAP mask only. We also study the asymmetry between the angular power spectra evaluated on the northern and southern hemispheres. When the features detected by needlets are masked, we find that the difference in the power, measured in terms of the anisotropy variance between ℓ = 4 and ℓ = 18, is reduced by a factor 2. We make available a mask related to needlet features for more detailed studies on asymmetries in the CMB anisotropy sky.
We present a comparison between three approaches to test non-Gaussianity of cosmic microwave back... more We present a comparison between three approaches to test non-Gaussianity of cosmic microwave background data. The Minkowski functionals, the empirical process method and the skewness of wavelet coefficients are applied to maps generated from non-standard inflationary models and to Gaussian maps with point sources included. We discuss the different power of the pixel, harmonic and wavelet space methods on these simulated almost full-sky data (with Planck like noise). We also suggest a new procedure consisting of a combination of statistics in pixel, harmonic and wavelet space.
We analyze the BOOMERanG 2003 (B03) 145 GHz temperature map to constrain the amplitude of a non G... more We analyze the BOOMERanG 2003 (B03) 145 GHz temperature map to constrain the amplitude of a non Gaussian, primordial contribution to CMB fluctuations. We perform a pixel space analysis restricted to a portion of the map chosen in view of high sensitivity, very low foreground contamination and tight control of systematic effects. We set up an estimator based on the three Minkowski functionals which relies on high quality simulated data, including non Gaussian CMB maps. We find good agreement with the Gaussian hypothesis and derive the first limits based on BOOMERanG data for the non linear coupling parameter f NL as −300 < f NL < 650 at 68% CL and −800 < f NL < 1050 at 95% CL.
Monthly Notices of the Royal Astronomical Society: Letters, 2009
We apply the needlet formalism to the Wilkinson Microwave Anisotropy Probe 5-year data, looking f... more We apply the needlet formalism to the Wilkinson Microwave Anisotropy Probe 5-year data, looking for evidence of non-Gaussianity in the bispectrum of the needlet amplitudes. We confirm earlier findings of an asymmetry in the non-Gaussianity between the northern and southern galactic hemispheres. We attempt to isolate which scales and geometrical configurations are most anomalous, and find the bispectrum is most significant on large scales and in the more co-linear configurations, and also in the 'squeezed' configurations. However, these anomalies do not appear to affect the estimate of the non-linear parameter f NL , and we see no significant difference between its value measured in the two hemispheres.
Monthly Notices of the Royal Astronomical Society, 2005
We use the PSCz galaxy redshift catalogue combined with constrained simulations based on the IRAS... more We use the PSCz galaxy redshift catalogue combined with constrained simulations based on the IRAS 1.2 Jy galaxy density field to estimate the contribution of hot gas in the local universe to the SZ-effect on large scales. We produce a full sky Healpix map predicting the SZ-effect from clusters as well as diffuse hot gas within 80 h −1 Mpc. Performing cross-correlation tests between this map and the WMAP data in pixel, harmonic and wavelet space we can put an upper limit on the effect. We conclude that the SZ effect from diffuse gas in the local universe cannot be detected in current CMB data and is not a contaminating factor on large scales (ℓ < 60) in studies of the CMB angular anisotropies. However, for future high sensitivity experiments observing at a wider range of frequencies, the predicted large scale SZ effect could be of importance.
Monthly Notices of the Royal Astronomical Society, 2005
We test the consistency of estimates of the non-linear coupling constant f NL using non-Gaussian ... more We test the consistency of estimates of the non-linear coupling constant f NL using non-Gaussian CMB maps generated by the method described in (Liguori, Matarrese & Moscardini 2003). This procedure to obtain non-Gaussian maps differs significantly from the method used to obtain f NL in previous works. Nevertheless, using spherical wavelets we find results in very good agreement with (Mukherjee & Wang 2004), showing that the two ways of generating primordial non-Gaussian maps give equivalent results. Moreover, we introduce a new method for estimating the non-linear coupling constant from CMB observations by using the local curvature of the temperature fluctuation field. Using this method, we estimate f NL = 30 ± 210 at the 2σ level. We present both Bayesian credible regions (assuming a flat prior) and proper (frequentist) confidence intervals on f NL , and discuss the relation between the two approaches. The two procedures produce markedly different outcomes, proving that a careful analysis on their different interpretations is needed.
Monthly Notices of the Royal Astronomical Society, 2010
We constrain the amplitude of primordial non-Gaussianity in the cosmic microwave background data ... more We constrain the amplitude of primordial non-Gaussianity in the cosmic microwave background data taking into account the presence of foreground residuals in the maps. We generalize the needlet bispectrum estimator marginalizing over the amplitudes of thermal dust, free-free and synchrotron templates. We apply our procedure to Wilkinson Microwave Anisotropy Probe 5-year data, finding f NL = 38 ± 47 (1σ), while the analysis without marginalization provides f NL = 35 ± 42. Splitting the marginalization over each foreground separately, we found that the estimates of f NL are positively cross-correlated of 17 and 12 per cent with the dust and synchrotron, respectively, while a negative cross-correlation of about −10 per cent is found for the free-free component.
Monthly Notices of the Royal Astronomical Society, 2010
We test the asymmetry of the cosmic microwave background anisotropy jointly in temperature and po... more We test the asymmetry of the cosmic microwave background anisotropy jointly in temperature and polarization. We study the hemispherical asymmetry, previously found only in the temperature field, with respect to the axis identified by Hansen et al. To this extent, we make use of the low-resolution Wilkinson Microwave Anisotropy Probe 5-yr temperature and polarization N side = 16 maps and our implementation of an optimal power spectrum estimator. We consider two simple estimators for the power asymmetry and we compare our findings with Monte Carlo simulations which take into account the full noise covariance matrix. We confirm an excess of power in temperature angular power spectrum in the Southern hemisphere at a significant level, between 3σ and 4σ depending on the exact range of multipoles considered. We do not find significant power asymmetry in the gradient (curl) component EE (BB) of polarized angular spectra. Furthermore, cross-correlation power spectra, i.e. TE, TB, EB, show no significant hemispherical asymmetry. We also show that the cold spot found by Vielva et al. in the Southern Galactic hemisphere does not alter the significance of the hemispherical asymmetries on multipoles which can be probed by maps at resolution N side = 16. Although the origin of the hemispherical asymmetry in temperature remains unclear, the study of the polarization pattern could add useful information on its explanation. We therefore forecast by Monte Carlo the Planck capabilities in probing polarization asymmetries.
Monthly Notices of the Royal Astronomical Society, 2010
The parity symmetry of the cosmic microwave background (CMB) pattern as seen by Wilkinson Microwa... more The parity symmetry of the cosmic microwave background (CMB) pattern as seen by Wilkinson Microwave Anisotropy Probe 7 yr (WMAP 7 yr) is tested jointly in temperature and polarization at large angular scale. A quadratic maximum likelihood (QML) estimator is applied to the WMAP 7-yr low-resolution maps to compute all polarized CMB angular power spectra. The analysis is supported by 10 000 realistic Monte Carlo realizations. We confirm the previously reported parity anomaly for TT in the range δ = [2, 22] at >99.5 per cent C.L. No anomalies have been detected in TT for a wider range (up to max = 40). No violations have been found for EE, TE and BB which we test here for the first time. The cross-spectra TB and EB are found to be consistent with zero. We also forecast Planck capabilities in probing parity violations on low-resolution maps.
Monthly Notices of the Royal Astronomical Society, 2006
We propose a fast and efficient bispectrum statistic for cosmic microwave background (CMB) temper... more We propose a fast and efficient bispectrum statistic for cosmic microwave background (CMB) temperature anisotropies to constrain the amplitude of the primordial non-Gaussian signal measured in terms of the non-linear coupling parameter f NL. We show how the method can achieve a remarkable computational advantage by focusing on subsets of the multipole configurations, where the non-Gaussian signal is more concentrated. The detection power of the test increases roughly linearly with the maximum multipole, as shown in the ideal case of an experiment without noise and gaps. The CPU-time scales as 3 max instead of 5 max for the full bispectrum, which for Planck resolution max ∼ 3000 means an improvement in speed of a factor of 10 7 compared with the full bispectrum analysis with minor loss in precision. This approach is complementary to the fast method introduced by Komatsu, Spergel & Wandelt using a reconstruction of the primordial fluctuation field. We find that the introduction of a galactic cut partially destroys the optimality of the configuration, which will then need to be dealt with in the future. We find for an ideal experiment with max = 2000 that upper limits of f NL < 8 can be obtained at 1σ. For the case of the WMAP experiment, we would be able to put limits of | f NL | < 40 if no galactic cut were present. Using the real data with a galactic cut, we obtain an estimate of −80 < f NL < 80 and −160 < f NL < 160 at 1 and 2σ , respectively.
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Papers by paolo cabella