Feb 1, 2018
How black holes shape the cosmos
A realistic universe out of the computer
At its intersection points, the cosmic web of gas and dark matter predicted by IllustrisTNG hosts galaxies quite similar to the shape and size of real galaxies. For the first time, hydrodynamical simulations could directly compute the detailed clustering pattern of galaxies in space. Comparison with observational data -- including newest large surveys -- demonstrate the high degree of realism of IllustrisTNG. In addition, the simulations predict how the cosmic web changes over time, in particular in relation to the underlying "back bone" of the dark matter cosmos. "It is particularly fascinating that we can accurately predict the influence of supermassive black holes on the distribution of matter out to large scales," says principal investigator Prof. Volker Springel (HITS, MPA, Heidelberg University). "This is crucial for reliably interpreting forthcoming cosmological measurements."
The most important transformation in the life cycle of galaxies
In another study, Dr. Dylan Nelson (MPA) was able to demonstrate the important impact of black holes on galaxies. Star-forming galaxies shine brightly in the blue light of their young stars until a sudden evolutionary shift ends the star formation, such that the galaxy becomes dominated by old, red stars, and joins a graveyard full of "red and dead" galaxies. "The only physical entity capable of extinguishing the star formation in our large elliptical galaxies are the supermassive black holes at their centers," explains Nelson. "The ultrafast outflows of these gravity traps reach velocities up to 10 percent of the speed of light and affect giant stellar systems that are billions of times larger than the comparably small black hole itself."
Where the stars sparkle: New findings for the structures of galaxies
IllustrisTNG also improves researchers´ understanding of the hierarchical structure formation of galaxies. Theorists argue that small galaxies should form first, and then merge into ever larger objects, driven by the relentless pull of gravity. The numerous galaxy collisions literally tear some galaxies apart and scatter their stars onto wide orbits around the newly created large galaxies, which should give them a faint background glow of stellar light. These predicted pale stellar halos are very difficult to observe due to their low surface brightness, but IllustrisTNG was able to simulate exactly what astronomers should be looking for in their data. "Our predictions can now be systematically checked by observers," Dr. Annalisa Pillepich (MPIA) points out, who led a further IllustrisTNG study. "This yields a critical test for the theoretical model of hierarchical galaxy formation."
Read more at Science Daily