Category: Media Coverage

Managing the huge volumes and varying streams of Big Data digital information presents formidable analytical challenges to anyone wanting to make sense of it. Consider the mapping of space, where scientists collect, process and transmit giga-scale data sets to generate accurate visual representations of millions of galaxies. Or consider the vast information being generated by genomics and bioinformatics as genomes are mapped and new drugs discovered. And soon the Internet of Things will bring millions of interconnected information-sensing and transmitting devices.

The new international projects, such as the Euclid space telescope, are ushering in the era of Big Data for cosmologists. Our questions about dark matter and dark energy, which on their own account for 95% of the content of our Universe, throw up new algorithmic, computational and theoretical challenges. The fourth concerns reproducible research, a fundamental concept for the verification and credibility of the published results.

La Direction de la recherche fondamentale au CEA lance le projet COSMIC, né du rapprochement de deux compétences en traitement des données localisées à l’Institut des sciences du vivant Frédéric-Joliot (NeuroSpin) et au CEA-Irfu (CosmoStat). Les mécanismes d’acquisition de données en radio-astronomie et en IRM présentent des similarités. Les modèles mathématiques utilisés sont en effet basés sur les principes de parcimonie et d’acquisition comprimée, dérivés de l’analyse harmonique.

​A key challenge in cosmological research is how to extract the most important information from satellite imagery and radio signals. The difficulty lies in the systematic processing of extremely noisy data for studying how stars and galaxies evolve through time. This is critical for astrophysicists in their effort to gain insights into cosmological processes such as the characterisation of dark matter in the Universe. Helping scientists find their way through this data maze is DEDALE, an interdisciplinary project that intends to develop the next generation of data analysis methods for the new era of big data in astrophysics and compressed sensing.

Today marks the release of the first papers to result from the XXL survey, the largest survey of galaxy clusters ever undertaken with ESA’s XMM-Newton X-ray observatory. The gargantuan clusters of galaxies surveyed are key features of the large-scale structure of the Universe and to better understand them is to better understand this structure and the circumstances that led to its evolution. The first results from the survey, published in a special issue of Astronomy and Astrophysics, hint at the answers and surprises that are captured in this unique bank of data and reveal the true potential of the survey.

In a review article in “Reports on Progress in Physics“, Martin Kilbinger of Astrophysics Department – AIM Laboratory at CEA-IRFU presents a comprehensive assessment of the results obtained from observations of the cosmic shear in the last 15 years. The cosmic shear effect has been measured for the first time in 2000. This effect is a distortion of the images of galaxies under the effect of gravity of the intervening clumps of matter. It allows to map the dark matter but also to determine how dark energy affects the cosmic web. The article highlights the most important challenges for turning cosmic shear into an accurate tool for cosmology. So far, dark matter has been mapped for only a tiny fraction of the sky. Future observations, such as those of the future space mission Euclid, will cover most accessible regions of the sky. The review presents the progress expected from these potential future missions for our understanding of the cosmos.

I l y a 13,8 milliards d’années naît l’Univers, sous la forme d’une singularité évoluant instantanément en un brouillard chaud, opaque, fait de noyaux d’hydrogène et d’électrons. Pendant plus de 300000 ans, ce plasma s’étend, par inflation•, mais les grains de lumière émis, les photons, sont aussitôt réabsorbés par les particules de matière. L’Univers est alors une véritable purée de pois. Puis vient le moment, en l’an 380000 après le big bang, où il est suffisamment dilaté et refroidi pour que les photons puissent se « libérer »: le cosmos devient transparent, la première lumière jaillit. Et c’est une image de cette toute première lumière, appelée fond diffus cosmologique (voir encadré), qu’ont publiée des chercheurs de l’École polytechnique fédérale de Lausanne (EPFL)1 et du CEA-Irfu. D’une précision exceptionnelle, elle a été reconstruite à partir des données enregistrées par les télescopes spatiaux WMAP et Planck, à l’aide de méthodes mathématiques très poussées.

Deux Monstres Cosmiques Annihilés, un traitement numérique a <<nettoyé>> les images du fond cosmique d’artifacts inexplicables.

An international collaboration of astrophysicists, led by Martin Kilbinger from the Astrophysics Division – AIM Laboratory AIM at CEA Saclay-Irfu and the Institute of Astrophysics Paris, has obtained the largest survey of galaxy images that are deformed by gravitation.
More than 4.2 million galaxies have been observed during more than 500 nights at the Canada-France Hawaii Telescope (CFHT) with the camera MegaCam, built at the CEA. The fine analysis of these images is the goal of the CFHTLenS project [1]. The very small distortions of galaxy images allowed to determine the fraction of dark matter and dark energy in a slice of the Universe between 2.4 and 8.8 billion years in the past, with a unprecedented level of precision. These results are complementary to those recently obtained by the Planck satellite at great distances from the analysis of the diffuse microwave background. This work is in press in the journal Monthly Notices of the Royal Astronomical Society (2013).