Star Birthing in Violent Galaxy Mergers

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When two galaxies collide, astronomers witness a frenzy of star formation creating what are known as “starburst galaxies.” Although this is known, it’s a little counter-intuitive; during galactic mergers, the swirling interstellar gases are so turbulent that star formation should be switched off. So what’s going on?

VIDEO: We’ve Simulated The ENTIRE Universe

Using two of Europe’s most powerful supercomputers, French astrophysicists simulated 300,000 light-years of interstellar gas inside a Milky Way-like galaxy (on the TGCC Curie supercomputer in France) and a volume of gas, 600,000 million light-years wide, inside two merging galaxies (on the SuperMUC supercomputer in Germany). Committing millions of hours of computational time, the simulation replicated the random motions of gas inside the galactic disks, resolving chaotic features fractions of a light-year across.

A frame from the simulation of the two colliding ‘Antennae’ galaxies. Here the galaxies are re-shaped after their first encounter. High resolution allows the astrophysicists to explore the smallest details. Stars are formed in the densest regions (yellow and red) under the effect of compressive turbulence. Star formation is more efficient here than in normal galaxies like our Milky Way.
Credit: F. Renaud/CEA-Sap

It is known that dense clouds of interstellar gas can collapse under mutual gravity, eventually sparking fusion and new stars. But in the turbulent wake of a galactic merger, star formation should be hindered, not accelerated. Turbulence should disrupt star forming regions, fragmenting the cloud. As these simulations prove, however, it is this turbulence that actually accelerates star birth, driving starburst galaxies.

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The researchers were able to compare the two simulations, showing that in the collision model, violent turbulence makes interstellar gases ripe for compression (and not dispersion), accelerating star birth.

“This is a big step forward in our understanding of star formation, something only made possible by the similarly major and parallel advances in computing power,” said lead researcher Florent Renaud of the AIM institute near Paris. “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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Like the recent supercomputer simulation that was used to model the evolution of our Universe, this example once again proves that despite the incredible complexities that underlie astrophysical processes, computing power is rapidly becoming more capable, allowing us a high-resolution glimpse at what drives the inner dynamics of starburst galaxies.

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