A Search for Dust Clouds near the Solar System with the Wilkinson Microwave Anisotropy Probe
Final Report Abstract
In this project, we planned to search for Solar system dust clouds in the WMAP data and to investigate if these clouds could resolve anomalies observed in the WMAP maps of the cosmic microwave background at large angular scales. We did not manage to resolve the issue of the WMAP anomalies, but we could exclude several of the proposed solutions, namely interstellar dust trapped in the heliosphere, as those dust grains would not be sufficiently large, and ring-like dust belts, as they won’t be able to explain the observed alignment and ratios of power between multipoles at the same time. We confirmed our hypothesis that Solar system dust is of concern to high precision measurements of the CMB, as it is possible that components invisible in the “classical” dust channels, show up in the frequency bands dominated by the CMB as one of several subdominant components. We also established that the ILC map (used by the WMAP team for their analysis of the largest angular scales) itself is not statistically isotropic, as it correlates with the orientation of the Milky Way, and thus should not be trusted at and below the 10µK level, the level of microwave radiation that could also stem from Solar system dust. An attempt to reconstruct a full sky map from the region outside the Milky Way was shown to produce a biased estimate — the large scale correlations are biased towards larger values. The release of full Planck data in January 2013 promises to provide a fresh perspective on the largest angular scales (note that these are the largest scales in the Universe that we can probe in principle and we must not take the luxury to simply ignore them). First of all, Planck can confirm or refute the existence of these anomalies. If they prevail, Planck will add new information in the Wien regime of the black body spectrum of the CMB, where Solar system dust would have a hard time to hide. We believe that the results of this project will provide a sound basis for Planck searches for Solar system dust and the resolution of the WMAP anomalies.
Publications
- No large-angle correlations on the non-Galactic microwave sky, Mon. Not. R. Astron. Soc. 399 (2009) 295
C.J. Copi, D. Huterer, D.J. Schwarz and D.G. Starkman
- The local dust foregrounds in the microwave sky. I. Thermal emission spectra, Astrophys. J. 705 (2009) 770
V. Dikarev, O. Preuss, S. Solanki, H. Krüger and A. Krivov
- Large angle anomalies in the CMB, Adv. Astron. 2010 (2010) 847541
C.J. Copi, D. Huterer, D.J. Schwarz and G.D. Starkman
- Bias in low-multipole CMB reconstructions. Mon. Not. R. Astron. Soc. 418 (2011) 505
C.J. Copi, D. Huterer, D.J. Schwarz and G.D. Starkman
