Universe anisotropies probed by the alignment of structures in the CMB

1. Universe anisotropies probed by the alignment of structures in the CMB Wiaux, Vielva, Martínez-González & Vandergheynst, 2006, PRL Patricio Vielva Astrophysics Department (IFCA, Santander) Currently visitor @ Astrophysics Group (Cavendish Lab., Cambridge) Bernard’s Cosmic Stories June 2006, Valencia

2. Outline of the talk • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

3. (from Copi et al. 2005) (from Hansen et al. 2004) Motivation • Many works have analysed the WMAP data for studying whether it is consistent with the isotropy principle. • Some works based on wavelets have detected a very large and very cold spot in the southern hemisphere showing a significant deviation from an isotropic GRF (Vielva et al. 2004, Cruz et al. 2005, 2006). • Certain analyses find a strong evidence for a north-south asymmetry maximized in a coordinate system with the north poleclose to the north ecliptic pole (e.g. Eriksen et al. 2004, Hansen et al. 2004, Land & Magueijo 2005a). • Other works find an anomalous alignment between the low multipoles of the CMB, suggesting a preferred direction near the ecliptic plane and close to the axis of the dipole (e.g. Copi et al. 2004,2005, Schwarz et al. 2004, de Oliveira-Costa et al., Land & Magueijo 2005b). • Some authors have not found any strong evidence for the isotropy violation (e.g. Hajian et al. 2005) • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

4. Our approach: the CMB structures can "watch" • Considering the previous results, we propose an alternative method for probing the statistical isotropy of the CMB • it relies on the analysis of the alignment of structures on the CMB • preferred directions in the universe are defined as the directions towards which local features of the CMB are mostly oriented • the number of times a direction is “watched” represents a signal on the sphere, D(w), allowing also for the analysis of its corresponding angular power spectrum • the analysis is feasible thanks to the steerable wavelet decomposition of the data, which also allows to probe different scales of the features • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

5. Greatcircle Seen twice Greatcircle Our approach: the CMB structures can "watch" • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Modified from the Max Tegmark web site An even signal is obtained Bernard’s Cosmic Stories June 2006, Valencia

6. Steerable wavelets • The wavelet transform of a signal gives us information about: • the scale of the structures presented in the signal • the position in which those structures are located • and (for the continuous case) it is obtained by convolving the signal with the wavelet. • Steerable wavelets are the natural extension of isotropic and directional wavelets, which have been successfully and extensively applied to many different topics within the CMB data analysis. • The steerable wavelets were introduced by Freeman & Adelson at the fall of the 80’s and the rise of the 90’s. They have been recently extended to the sphere by Wiaux et al. 2005. • They appear as a solution for the multi-directional image analysis: any direction can be explored through a linear combination of a given basis. • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

7. Steerable wavelets • The wavelet coefficient at a given position (x, y), at a given scale (R)and at a particular orientation (c), can be expressed as: • Their properties allows to explore possibilities that are (in practice) unfeasible by using standard techniques, like the one proposed in this work: the anisotropy analysis by studying the alignment of the CMB structures. • Typical examples of steerable wavelets are the Nth-directional derivatives of a Gaussian function • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

8. Steerable wavelets An example: the 2nd derivative of a Gaussian • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

9. Orientation given the maximum of the wavelet coefficient: Orientation of the maximum value of the wavelet coefficients Orientation of the feature Steerable wavelets • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions By computing three wavelet coefficient maps (for each scale), the local orientation that better matches that of the CMB features can be obtained Bernard’s Cosmic Stories June 2006, Valencia

10. { , , ...} Steerable wavelets • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

11. Steerable wavelets Wavelet coefficients matching the features orientations Number of times that a position is “watched” by the features • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

12. Application to the WMAP data • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Any preferred direction in the sky? WMAP web site Bernard’s Cosmic Stories June 2006, Valencia

13. Application to the WMAP data The analysed map is the one proposed by Komatsu et al. 2003 (NG paper of WMAP-1st yr). The map is degraded down to Nside=32. The Kp0 mask is applied. Scales from 5 to 30 degrees are explored. • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

14. Application to the WMAP data DR(w) map for the co-added WMAP map @ 8.3º angular size given in terms of the 1 – p-value (estimated from 10000 simulations) • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

15. Normal direction to the detected plane Dipole direction NEP Application to the WMAP data There are 20 anomalous directions in the sky, that have been “watched” more times than any of the analysed simulations. The probability of having, at least, this number of so “watched” positions is 0.01 % • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions This results synthesises previous anomalies !! Best fit of a great circle passing by the anomalous directions Bernard’s Cosmic Stories June 2006, Valencia

16. Q band V band W band Application to the WMAP data Co-added DR(w) map for the co-added WMAP map @ 8.3º angular size given in terms of the #s (estimated from 10000 simulations) • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

17. Application to the WMAP data Are those anomalous directions due to an specific “watching” of certain structures located in specific places? Or, on the contrary, they come from positions on the sky homogenously distributed? • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions ? Bernard’s Cosmic Stories June 2006, Valencia

18. Application to the WMAP data 1yr • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Same structures are found, but signification decreases: from 0.01% to 0.42% 3yr Bernard’s Cosmic Stories June 2006, Valencia

19. What next? • Current work is in progress to find the possible source of this anisotropy detection: • the coincidence of the preferred directions detected with the EP and dipole axes suggest possible unknown systematics • the angular size in which the preferred directions appear is compatible with topological defects (like textures) or secondary anisotropies due to the Rees-Sciama effect • although the detected anisotropy seems to be the same at all the frequencies, it must be also considered that foregrounds could generate aligned structures of several degrees • the analysis of the angular power spectrum of D(w)could help to study the multipole distribution of the anomalies • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Bernard’s Cosmic Stories June 2006, Valencia

20. Conclusions • A new approach based on the alignment of the CMB structures has been proposed for studying the isotropic principle. • The method relies in the application of steerable wavelets, that allows to identified the local orientation of the features at each scale. • The application to the 1st yr-WMAP data shows that, at scales of 8.3º (multipole range between l=11 and l=27), 20 anomalous directions are detected. • Those directions identified, first, a plane which perpendicular direction is close to the dipole axis, and second, a most prominent position on that plane that is extremely close to the NEP. • This result has been confirmed with the second WMAP release. • Further analysis is needed to identify the possible source of this anisotropy. • Steerable wavelets open a door to fast oriented multi-scale analyses of the CMB • Motivation • Our approach: the CMB structures can "watch" • Steerable wavelets • Application to the WMAP data • What next? • Conclusions Thank you for your attention! Bernard’s Cosmic Stories June 2006, Valencia