Cosmic Microwave Background: Large Scale Non Gaussianities Studies

Cosmic Microwave Background: Large Scale Non Gaussianities Studies


If the LGMCA map (Bobin et al, A&A, 2014) presented above is used, then LCS has shown that this map is clean enough so no masking  is required anymore for large scale statistical analysis. We have found the most claimed anomalies in the CMB map disappear if i) we do not mask, and ii) we take  properly into account the Integrated Sachs-Wolfe effect (ISW) (Rassat and Starck, 2013). Similar results were obtained with Planck data and CMB large scales are therefore compatible with the standard l-CDM cosmological model (Rassat et al, 2014).  

Reference 1: A. Rassat, J-L. Starck, P. Paykari, F. Sureau and J. Bobin, "Planck CMB Anomalies: Astrophysical and Cosmological Foregrounds and the Curse of Masking",Journal of Cosmology and Astroparticle Physics, 08, id. 006, 2014.

Reference 2: A. Rassat and J-L. Starck, "On Preferred Axes in WMAP Cosmic Microwave Background Data after Subtraction of the Integrated Sachs-Wolfe Effect", Astronomy and Astrophysics, 557, id.L1, pp 7, 2013.

Press release 1: Science et Vie, August 2014.

Press release 2: Défis du CEA, March, 2015.

CFHTLenS: Constraining the Dark Universe with CFHTlenS Weak Lensing Survey

CFHTLenS: Constraining the Dark Universe with weak lensing from the CFHT Lensing Survey


We have taken part in the largest galaxy survey to measure the distribution of dark matter in the Universe using the gravitational lensing effect. More than 4.2 million galaxies have been observed for over 500 nights at the Canada-France Hawaii Telescope (CFHT) with the camera MegaCam, built at the CEA. Measuring the weak-lensing distortions from these galaxies, we determined the fraction of dark matter and dark energy up to 8.8 billion years in the past. Together with other experiments the results showed that the Universe is undergoing a phase of accelerated expansion, due to a yet unknown “dark-energy” component, that makes up around 70% of the cosmos. Those measurements were also use to test the laws of gravity on large scales. Some models of deviations from Einstein’s theory of general relativity could be ruled out by the data, reducing possible alternatives for the cause of the accelerated expansion of the Universe.

Reference 1: Kilbinger et al, CFHTLenS: combined probe cosmological model comparison using 2D weak gravitational lensing, MNRAS, 3, 2200-2220, 2013

Reference 2: Simpson F, Heymans C, Parkinson D, Blake C, Kilbinger M & al. 2013 MNRAS 429, 2249–2263

Press release:  http://irfu.cea.fr/Sap/en/Phocea/Vie_des_labos/Ast/ast.php?id_ast=3281