News 2015

Jul 28, 2015
Cosmology with cosmic shear observations

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.

See the presentation by Martin Kilbinger

Dec 15, 2015
3D-maps of galaxy clusters

A new 3D map of galaxy clusters has just been published by a research team led by Maguerite Pierre from the Astrophysics Department-AIM Laboratory of CEA-IRFU through a survey of two regions of the sky, each covering about 25 square degrees (about 100 times the area of ​​the full moon). The survey, called XXL, was conducted from 2011 to 2013 resulting from 543 observations of the X-ray satellite XMM-Newton and requiring over 6 million seconds exposure. The XXL survey helped to locate and identify 450 clusters of galaxies and 22 000 active galaxies. Galaxy clusters are the largest structures in the Universe, reaching masses of over a hundred thousand billion times the Sun's mass. Their number and distribution were studied up to distances of about 7 billion light-years when the universe was half its present age. The XXL survey found a significantly lower cluster density than predicted by cosmological models and a quantity of gas in these clusters also lower than expected. It also allowed the discovery of five new super-cluster or clusters of clusters of galaxies. These preliminary results are subject to a first series of 13 articles, published in a special issue of the journal Astronomy & Astrophysics (in press).

Jul 28, 2015
Cosmology with cosmic shear observations

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.

See the presentation by Martin Kilbinger
May 07, 2015
A key for unsderstanding galaxy evolution

As part of an observing program carried out with the Hubble Space Telescope, a group of researchers from the “Service d’Astrophysique-Laboratoire AIM” of CEA-IRFU led by Anita Zanella discovered the birth cry of a massive star-forming clump in the disk of a very distant galaxy. This giant clump is less than 10 million years old, and it is the very first time that such a young star-forming region is observed in the distant Universe. This discovery sheds new light on how stars were born within distant galaxies. The physical properties of this object reveal that newly-born clumps in such galaxies survive from stellar winds and supernovae feedback, and can thus live for a few hundred million years unlike the predictions from several theoretical models. Their long lifetime could enable their migration toward the inner regions of the galaxy, hence contributing to the total mass of the galactic bulge and the growth of the central black hole. These results are published in the “Nature” journal from May 2015.

Jun 22, 2015
The enigma of the quasi-periodic oscillations

A team of researchers from CEA (Astrophysical Department and CEA-DAM) and the LUTH Laboratory (Paris Observatory) has just published a comprehensive study of an enigmatic phenomenon of quasi-periodic oscillations at the surface of strongly magnetic white dwarfs also called "Polars ". These dense stars are orbiting a companion and capture its material that falls freely toward the white dwarf poles. Strongly heated to millions of degrees, the hot gas or plasma then emits mainly in X-rays. Thanks to detailed numerical simulations of the plasma behavior, the researchers were able to reconstruct the existence of strong instabilities leading to rapid oscillations in the luminosity with timescales of only a few seconds. However, using the database of the XMM-Newton satellite, these oscillations were sought unsuccessfully by the team, in the X-ray emission of over 20 Polars. This contradiction leads today researchers to propose to study the phenomenon in the laboratory. Indeed, similar physical conditions can currently be replicated by large power lasers like the LMJ [1]. The control of plasma instabilities is a key element for nuclear fusion by magnetic (ITER experience) ou inertiel confinement (laser Mégajoule) and instabilities of white dwarfs could contribute to a better understanding of this general phenomenon. These results are the subject of two articles published in the journal Astronomy & Astrophysics, July 2015.

 

see the movie of the numerical simulation (short version)

 

Retour en haut