Realistic Galaxy Simulations: It's All About Passing Wind
Computer simulations of the Universe have recently been able to finally simulate the characteristics of real galaxies by tweaking the Galactic Wind.
I love computer simulations. They’re kinda like grandmas.
Generally speaking, if you can successfully explain something arcane to your grandma, then you probably have a decent understanding of the topic. Historically, this has not been the case with simulations of galaxies. Many different types of astronomical simulations have been successful and illuminating but galaxies themselves didn’t really match up to reality.They were either too small or too big. If not that, then they were probably too old or too perfectly spherical.
Just like grandma then, if the computer simulation couldn’t grow a galaxy that matches our observations, then the computer wasn’t being told everything it needed to know to fully understand and hence recreate them.
This is where the EAGLE simulation comes in. That stands for Evolution and Assembly of GaLaxies and their Environments. This simulation was run by an international team of astronomers representing the Universities of Leiden in the Netherlands and Durham in the UK.
Simulating a universe for galaxies to gestate in can’t be done in some smartphone app (yet). It took 2 supercomputers months to pull this off. One of them is called The Cosmology Machine (Cosma) which is based in Durham University and packs a respectable punch at 182 trillion operations per second. The other supercomputer is even more impressive. It’s called Curie (you can probably guess where it’s housed) and it boasts a quite formidable top speed of 2 Petaflops or 2 quadrillion operations per second.
Tons of processing power is useless of course if you just recreate the fundamental programming problems that other simulations encountered. To address this, the researchers tweaked a variable that seems to have been the root cause of previous simulation failures.Galactic Wind.
Galactic wind is the outflow of charged particles from a galaxy.They are primarily produced by large stars during the very early stages of their lives and the very end. Young massive stars produce profligate amounts of stellar wind. This wind can be produced in significant amounts especially when stars are created in quick succession during what’s called starbursts. Galactic winds can also be created during supernova explosions. Finally, actively feeding black holes can also make a contribution to the galactic winds ejected by a galaxy.
Incorporating galactic winds into universe simulations had been done before but apparently they were not as strong as they needed to be. In fact recent research has shown that these winds can extend thousands of light years beyond the parent galaxy and even fill up a space equivalent to the volume of the galaxy itself.
To see how this can determine the fate of a galaxy, consider why we don’t see many galaxies that are truly titanic in size. Galaxy clusters and simple gravity should make them common one would think. As a galaxy gets bigger, it has more raw material to form more stars. As starbursts occur however, galactic wind expels much of this extra material into intergalactic space. This creates a feedback that tends to mitigate the continued growth of the galaxy and the formation of gigantic galaxies.
When simulated galaxies have the appropriate level of galactic wind then, they tend to be smaller and younger because stars form later and in fewer quantities. This is exactly what astronomers see when they look at real galaxies.
Future work will likely involve the study of galaxy formation in detail which is now possible since our simulations can now replicate what we observe.
Co-author of the study, Rob Crain said:
“This is the start of a new era for us. We can now manipulate the conditions of the universe and study the evolution of galaxies throughout the past 14 billion years”
Now if we could only get that simulation to talk to grandma.
Image Credit: ESA/AOES Medialab