Three colour (BVI) image of a distant overdense region of galaxies taken by the Hubble Space Telescope. The image is focused on a spiral galaxy similar to the Milky Way but located at z = 1, i.e. 8 billion years ago. Twice the mass of the Milky Way, it has a star formation rate thirty times higher due to the surrounding galaxy overdensity.
Observational Cosmology has reached an important turning point. After years of seeking the parameters that govern the evolution of the Universe, there seems to be increasing consensus in acknowledging the dominant influence of dark matter on baryons and that of dark energy on dark matter. Paradoxically, the behaviour of the two “dark” components that make up 95% of the energy content of the Universe is easy to model (dark matter is nondissipative and subject only to gravity, while dark energy acts as an anti-gravitational factor), even though our knowledge of their nature remains highly speculative. This has led to the scientific community’s leaning increasingly toward what has become the conundrum that best stands up to theoretical attack: the behaviour of baryons and the origin of the light we receive from stars, galaxies and galaxy clusters. It is now acknowledged that it is not possible to understand how galaxies form and evolve without using the entire electromagnetic spectrum to study their various components (stars, gasses and dust) in their different states (neutral, ionized, young/old, dense/not very dense).
last update : 10-18 00:00:00-2005 (604)
Quantification of the star-formation and black-hole growth rate in galaxies Until the middle of the last decade, mergers of galaxies and the star formation episodes triggered by these phenomena had been considered as a major, even dominant, ... More »
The giant gas ring in Leo, formed when two galaxies collided
An international team led by astrophysicists from the Lyon Observatory (CRAL, CNRS/INSU, Université Lyon 1) and the AIM laboratory (CEA-Irfu, CNRS, Université Paris 7) has just shed some light on the origins of the giant gas ring in ... More »
The most famous collision of galaxies decoded using ‘high-resolution’ simulations
‘High-resolution’ numerical simulations carried out by scientists at the Astrophysics Department of the CEA-Irfu/AIM have just revealed that the most famous galactic collision ever, the Antennae collision, produces far more stars ... More »
The dark galaxy may just be tidal debris (15 novembre 2007)
What is a galaxy ? Stars, gas, some dust and surrounding them an invisible dark matter halo. The discovery a few years ago of a so-called « dark galaxy » devoid of its most famous component - the stars - raised a lot of interest in ... More »
The hot gas found in stars produced by laser pulses
A major international collaboration , involving researchers from the CEA-IRFU Astrophysics Department, CEA-IRAMIS and CEA-DAM, has succeeded in measuring for the first time the effects of light absorption by nickel in high temperature plasmas ... More »