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Simulations Reveal Why Galactic Collisions Result In Starbursts

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Justine Alford

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clockMay 13 2014, 14:42 UTC
914 Simulations Reveal Why Galactic Collisions Result In Starbursts
F. Renaud / CEA-Sap. A snapshot from the simulation of the collision between two Antennae galaxies. Stars form within the most dense regions (yellow and red) from the effects of compressive turbulence.

Through the use of sophisticated computer simulations, scientists believe that they have finally solved a mystery which has left astronomers scratching their heads for many years: why galactic collisions trigger surges of star formation, or starbursts. The results of the study are published in Monthly Notices of the Royal Astronomical Society.

Stars form within clouds of gas and dust that are dispersed throughout galaxies. More specifically, turbulence within these clouds results in the gas and dust collapsing under its own gravitational attraction, forming a hot core which will eventually become a star. When galaxies collide, or merge, a surge of gas inflow toward the center of the galaxy occurs which causes the gas to move in a more random fashion. This increase in turbulence should, in theory, disrupt the collapse of the cloud and thus prevent star formation, but in fact the opposite occurs.


In order to investigate why this might be happening, a team of French astrophysicists, led by Florent Renaud, turned to Europe’s most powerful supercomputers to model two different systems. The first, which required 12 million hours of computational time, involved modeling a galaxy similar to the Milky Way and simulated conditions across 300,000 light years. Next, the team modeled two colliding Antennae galaxies across 600,000 light years, which required 8 million computing hours. The high resolution of these models bestowed the scientists with a tremendous level of detail, which led to some interesting results.

The models demonstrated that when two galaxies collide, tidal compression is enhanced which causes alterations in the turbulence of the galactic gas. As oppose to spiraling around, the gas enters a compressive mode which results in an excess of dense gas. This gas eventually collapses and forms stars in both galaxies, and thus a starburst occurs.  

“This is a big step forward in our understanding of star formation, something only made possibly by the similarly major and parallel advances in computing power,” says Florent. “These systems are helping us unlock the nature of galaxies and their contents in ever more detail, helping astronomers to slowly assemble their complete history.” 

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