Oct 04, 2010
Message from the Antennae
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 than observations suggested. When two galaxies meet, the resulting gas compression causes the ignition of new stars. Until now, it seemed that these new stars appeared only in high-density regions, mainly near the core of the collision. A computer re-creation of the collision, with a sufficiently high resolution to pick out the smallest gas clouds for the first time, shows that the starburst is in fact distributed far more uniformly inside the large number of star superclusters scattered across the disks of the galaxies. This important result helps scientists to understand why, in certain collisions, around 100 to 1000 stars per year can appear at the same time. This work was published in Astrophysical Journal Letters.


High-resolution numerical simulation of the collision of two galaxies. The simulation models the movement of the galaxies’ gas during a 500-million-year period in a region measuring 600,000 light-years along each side. The disks of the two galaxies collide after 250 million years and then again after 450 million years. These collisions cause gas compression, resulting in the formation of new stars inside the points of light that are visible on the image. Credits: CEA-Irfu/SAp-AIM, COAST program. (If the video does not appear, click here). 


Meeting of two vessels of stars

A spiral galaxy appears to be a vast disk, with a radius of several tens of thousands of light-years, filled with gas and tens of billions of stars. While some old stars ‘die’ there, new stars are constantly being formed out of the gas. In an isolated spiral galaxy, on average a relatively small mass of gas, comparable to the mass of our Sun, is transformed into young stars at the center of small dense clouds. But when two galaxies collide, the impact is so violent that the formation of new stars is multiplied by ten. The gas is highly compressed, and instabilities then trigger the manufacture of new stars—sometimes as many as 100 or even 1000 solar masses per year. This is known as a starburst.

The most spectacular galactic collision of all is the ‘Antennae’ collision, in which two spiral galaxies of the Corvus constellation, NGC4038 and NGC4039, located approximately 62 million light-years from Earth, came into contact and grew two long arms of gas resembling the antennae of an insect. Astronomers estimate the current rate of star formation in the Antennae galaxy at three to 20 solar masses per year. Such estimates are difficult to make, however, because of the presence of dust that absorbs the radiation emitted by the stars, thus obscuring our view of the galaxies.


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Publications :

« The Driving Mechanism of Starbursts in Galaxy Mergers »
Teyssier, Romain (1,2); Chapon, Damien (1); Bournaud, Frédéric (1)
(1) Astrophysics division – AIM Laboratory, CEA Saclay,
(2) Institute for Theoretical Physics, University of Zürich
published in The Astrophysical Journal Letters, Volume 720, Issue 2, pp. L149-L154 (2010),
for an electronic version ficher PDF


To go further : l’actualité CNRS/INSU


You can read as well: - "Anneau de gaz et collision de galaxies" (30 juin 2010)
                                -  "Une nouvelle théorie pour la formation des galaxies"  (22 janvier 2009)



Written by: D. Chapon, J.M. Bonnet-Bidaud

#2905 - Last update : 10/04 2010


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