Frode K. Hansen

University of Oslo

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K. M. Górski

University of Warsaw

A. J. Banday

Université Toulouse III - Paul Sabatier

H. K. Eriksen

University of Oslo

Heliana E. Luparello

Consejo Nacional de Investigaciones Científicas y Técnicas

D. G. Lambas

Universidad Nacional de Córdoba

Y. Fantaye

African Institute for Mathematical Sciences

F. M. Toscano

Instituto de Astronomía Teórica y Experimental

Domenico Marinucci

University of Rome Tor Vergata

T. R. Jaffe

Goddard Space Flight Center

S. Scodeller

University of Oslo

Cooperative Institutions

University of Oslo

Centre National de la Recherche Scientifique

University of Rome Tor Vergata

University of Milan

Consejo Nacional de Investigaciones Científicas y Técnicas

Instituto de Astronomía Teórica y Experimental

Agenzia Spaziale Italiana

Aalto University

European Space Research Institute

Université de Toulouse

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Searches for violation of statistical isotropy: power asymmetry in WMAP and Planck sky maps as measured by a local variance estimator

cosp (2014)

Y. Akrami Y. Fantaye Arman Shafieloo Hans K. Eriksen Frode K. Hansen

CMB cold spot

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Radial 3D-Needlets on the Unit Ball

Proceedings of the International Astronomical Union (2014)

Claudio Durastanti Y. Fantaye Frode K. Hansen Domenico Marinucci Isaac Z. Pesenson

Abstract We present a simple construction of spherical wavelets for the unit ball, which we label Radial 3D Needlets. We envisage an experimental framework where data are collected on concentric spheres with the same pixelization at different radial distances from the origin. The unit ball is hence viewed as a tensor product of the unit interval with the unit sphere: a set of eigenfunctions is therefore defined on the corresponding Laplacian operator. Wavelets are then constructed by a smooth convolution of the projectors defined by these eigenfunctions. Localization properties may be rigorously shown to hold in the real and harmonic domain, and an exact reconstruction formula holds; the system allows a very convenient computational implementation.

Unit sphere

Eigenfunction

Ball (mathematics)

10.1017/s1743921314010801

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Are CMB derived cosmological parameters affected by foregrounds associated to nearby galaxies?

arXiv (Cornell University) (2024)

F. M. Toscano Frode K. Hansen D. G. Lambas Heliana E. Luparello P. Fosalba

We perform cosmological parameters estimation on Planck Cosmic Microwave Background (CMB) maps masking the recently discovered foreground related to nearby spiral galaxies. In addition, we also analyse the association between these foreground regions and recent claims of cosmological causal horizons in localized CMB parameter estimates. Our analysis shows consistent cosmological parameter values regardless of the masking approach, though reduced sky areas introduce larger uncertainties. By modelling the new extragalactic foreground, we identify a resemblance with local parameter variation maps with a statistical significance at the 3 sigma level, suggesting that a simplified foreground model partially accounts, (40-50)% correlation with 15% uncertainty, for the observed causal horizons. These findings add new evidence to the existence of the new foreground associated with large spiral galaxies and show that estimates of cosmological parameters on smaller patches on the sky can be largely affected by these foregrounds, but that the parameters taken over the full sky are unaltered.

10.48550/arxiv.2410.24026

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EXCESS ELLIPTICITY OF HOT AND COLD SPOTS IN THEWMAPDATA?

The Astrophysical Journal (2013)

Eirik Berntsen Frode K. Hansen

We investigate claims of excess ellipticity of hot and cold spots in the Wilkinson Microwave Anisotropy Probe (WMAP) data. Using the cosmic microwave background (CMB) data from 7 yr of observations by the WMAP satellite, we find, contrary to previous claims of a 10σ detection of excess ellipticity in the 3 yr data, that the ellipticity of hot and cold spots is perfectly consistent with simulated CMB maps based on the concordance cosmology. We further test for excess obliquity and excess skewness/kurtosis of ellipticity and obliquity and find the WMAP7 data consistent with Gaussian simulated maps.

CMB cold spot

Kurtosis

Cold spot

Cosmic background radiation

10.1088/0004-637x/779/1/37

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DIRECTIONAL DEPENDENCE OF ΛCDM COSMOLOGICAL PARAMETERS

The Astrophysical Journal Letters (2013)

M. Axelsson Y. Fantaye Frode K. Hansen A. J. Banday H. K. Eriksen

We study hemispherical power asymmetry in the Wilkinson Microwave Anisotropy Probe 9 yr data. We analyze the combined V- and W-band sky maps, after application of the KQ85 mask, and find that the asymmetry is statistically significant at the 3.4σ confidence level for ℓ = 2–600, where the data are signal-dominated, with a preferred asymmetry direction (l, b) = (227, −27). Individual asymmetry axes estimated from six independent multipole ranges are all consistent with this direction. Subsequently, we estimate cosmological parameters on different parts of the sky and show that the parameters As, ns, and Ωb are the most sensitive to this power asymmetry. In particular, for the two opposite hemispheres aligned with the preferred asymmetry axis, we find ns = 0.959 ± 0.022 and ns = 0.989 ± 0.024, respectively.

SIGNAL (programming language)

10.1088/2041-8205/773/1/l3

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Point Source Power in 3-year Wilkinson Microwave Anisotropy Probe Data

American Astronomical Society Meeting Abstracts (2006)

K. M. Huffenberger H. K. Eriksen Frode K. Hansen

Using a set of multifrequency cross spectra computed from the 3 year WMAP sky maps, we fit for the unresolved point-source contribution. For a white-noise power spectrum, we find a Q-band amplitude of A = 0.011 ± 0.001 μK^2 sr (antenna temperature), significantly smaller than the value of 0.017 ± 0.002 μK^2 sr used to correct the spectra in the WMAP release. Modifying the point-source correction in this way largely resolves the discrepancy that Eriksen et al. found between the WMAP V- and W-band power spectra. Correcting the co-added WMAP spectrum for both the low-l power excess due to a suboptimal likelihood approximation—also reported by Eriksen et al.—and the high-l power deficit due to oversubtracted point sources—presented in this Letter—we find that the net effect in terms of cosmological parameters is an ~0.7 σ shift in n_s to larger values. For the combination of WMAP, BOOMERANG, and ACBAR data, we find ns = 0.969 ± 0.016, lowering the significance of n_s ≠ 1 from ~2.7 σ to ~2.0 σ.

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No Higher Criticism of the Bianchi-corrected Wilkinson Microwave Anisotropy Probe data

Monthly Notices of the Royal Astronomical Society (2006)

L. Cayón A. J. Banday T. R. Jaffe H. K. Eriksen Frode K. Hansen

Higher Criticism (HC) has been proposed by Donoho & Jin as an effective statistic to detect deviations from Gaussianity. Motivated by the success of the Bianchi VIIh model in addressing many of the anomalies observed in the Wilkinson Microwave Anisotropy Probe (WMAP) data (Jaffe et al.), we present calculations in real and in wavelet space of the HC statistic of the Bianchi-corrected WMAP first-year data. At the wavelet scale of 5°, the HC of the WMAP map drops from a value above the 99 per cent confidence level (c.l.) to a value below the 68 per cent CL when corrected by the Bianchi template. An important property of the HC statistic is its ability to locate the pixels that account for the deviation from Gaussianity. The analysis of the uncorrected WMAP data pointed to a cold spot in the Southern hemisphere, centred at l∼ 209°, b∼−57°. The HC of the Bianchi-corrected map indicates that this spot remains prominent, albeit at a level completely consistent with Gaussian statistics. Consequently, it is debatable how much emphasis should be placed on this residual feature, but we consider the effect of modestly increasing the scaling of the template. A factor of only 1.2 renders the spot indistinguishable from the background level, with no noticeable impact on the results published in Jaffe et al. for the low-l anomalies, large-scale power asymmetry or wavelet kurtosis. A trivial interpretation would be that the Bianchi template may require a small enhancement of power on scales corresponding to the wavelet scale of 5°.

10.1111/j.1365-2966.2006.10381.x

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INTRODUCING MEXICAN NEEDLETS FOR CMB ANALYSIS: ISSUES FOR PRACTICAL APPLICATIONS AND COMPARISON WITH STANDARD NEEDLETS

The Astrophysical Journal (2011)

S. Scodeller Øystein Rudjord Frode K. Hansen Domenico Marinucci Daryl Geller

Over the last few years, needlets have a emerged as a useful tool for the analysis of Cosmic Microwave Background (CMB) data. Our aim in this paper is first to introduce in the CMB literature a different form of needlets, known as Mexican needlets, first discussed in the mathematical literature by Geller and Mayeli (2009a,b). We then proceed with an extensive study of the properties of both standard and Mexican needlets; these properties depend on some parameters which can be tuned in order to optimize the performance for a given application. Our second aim in this paper is then to give practical advice on how to adjust these parameters in order to achieve the best properties for a given problem in CMB data analysis. In particular we investigate localization properties in real and harmonic spaces and propose a recipe on how to quantify the influence of galactic and point source masks on the needlet coefficients. We also show that for certain parameter values, the Mexican needlets provide a close approximation to the Spherical Mexican Hat Wavelets (whence their name), with some advantages concerning their numerical implementation and the derivation of their statistical properties.

10.1088/0004-637x/733/2/121

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Citations (38)

Fast and Efficient Template Fitting of Deterministic Anisotropic Cosmological Models Applied toWMAPData

The Astrophysical Journal (2006)

T. R. Jaffe A. J. Banday H. K. Eriksen K. M. Górski Frode K. Hansen

We explore methods of fitting templates to cosmic microwave background (CMB) data, and in particular demonstrate the application of the total convolver algorithm as a fast method of performing a search over all possible locations and orientations of the template relative to the sky. This analysis includes investigation of issues such as chance alignments and foreground residuals. We apply these methods to compare Bianchi models of type VIIh to WMAP first-year data and confirm the basic result of our 2005 paper.

CMB cold spot

Template

Cosmic background radiation

10.1086/501343

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Citations (70)

DETECTION OF NEW POINT SOURCES INWMAP7 YEAR DATA USING INTERNAL TEMPLATES AND NEEDLETS

The Astrophysical Journal (2012)

S. Scodeller Frode K. Hansen Domenico Marinucci

We have developed a new needlet based method to detect point sources in cosmic microwave background (CMB) maps and have applied it to the WMAP 7 year data. We use both the individual frequency channels as well as internal templates, the difference between pairs of frequency channels, with the advantage that the CMB component is eliminated. Using the area of the sky outside the Kq85 galactic mask, we detect a total of 2102 point sources at the $5\sigma$ level in either the frequency maps or the internal templates. Of these, 1116 are detected either at $5\sigma$ directly in the frequency channels or at $5\sigma$ in the internal templates and $\geq3\sigma$ at the corresponding position in the frequency channels. Of the 1116 sources, 603 are detections which have not been reported so far in WMAP data. We have made a catalogue of these sources available with position and flux estimated in the WMAP channels where they are seen. In total, we identified 1029 of the 1116 sources with counterparts at 5GHz and 69 at other frequencies.

CMB cold spot

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Position (finance)

Cosmic background radiation

Sigma

10.1088/0004-637x/753/1/27

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Citations (13)