Photons from far-off light sources, like blazars, are capable of going up against a constant exchange of identity in their journey through the Universe just like a nail-biting thriller packed with escapes and subterfuge.
This is an operation that permits these extremely small particles of light to escape an enemy which, if stumbled upon, would crush them. This phenomenon has been studied by a team of Researchers from the University of Salento, Bari, the National Institute for Nuclear Physics (INFN), the National Institute for Astrophysics (INAF) and SISSA thanks to brand new simulation models capable of reproducing the complexity of the cosmos as never before.
Extremely high energy photons (gamma rays) should normally "collide" with the background light emitted by galaxies converted into pairs of matter and antimatter particles, as envisioned by the Theory of Relativity. It is for this reason that it is essential for the sources of very high energy gamma rays to appear considerably less bright than what is observed in a number of cases.
One possible explanation for this surprising anomaly refers to the fact that light photons are changed into hypothetical weakly-interacting particles, "axions" which, in turn, would transform into photons, because of the interaction with magnetic fields. With these metamorphoses, it is possible for a part of the photons to escape interaction with the intergalactic background light that is capable of making them disappear.
The study published In Physical Review Letters emphasizes the importance of this process, which re-created an extremely sophisticated model of the Cosmic Web, a network of filaments made up of gas and dark matter existing throughout the Universe and of its magnetic fields. The above-mentioned effects are now expecting comparison with those obtained experimentally via Cherenkov Telescope Array new generation telescopes.
In this research, through unprecedented and complex computer simulations made at the CSCS Supercomputing Centre in Lugano, Scholars have succeeded in reproducing the so-called Cosmic Web and the magnetic fields linked with this. This is in order to analyze the possibility, advanced from earlier theories, that photons from a light source are converted into axions, hypothetical elementary particles, when they interact with an extragalactic magnetic field.
It is now possible to retransform axions into photons by working together with other magnetic fields. Researchers Daniele Montanino, Franco Vazza, Alessandro Mirizzi and Matteo Viel explain, "Photons from luminous bodies disappear when they encounter extragalactic background light (EBL). But if on their journey they head into these transformations as envisaged by these theories, it would explain why, in addition to giving very important information on processes that occur in the universe, distant celestial bodies are brighter than expected from an observation on Earth. These changes would, in fact, enable a greater number of photons to reach the Earth."
In the simulations developed by Scientists, thanks to the wealth of magnetic fields existing in the Cosmic Web’s filaments reconstructed with the simulations, the conversion phenomenon would now seem to be much more applicable than predicted by earlier models, "Our simulations reproduce a very realistic picture of the cosmos’ structure. From what we have observed, the distribution of the Cosmic Web envisaged by us would markedly increase the probability of these transformations."
As a next step, the research will focus on comparing simulation results with the experimental data attained by employing the Cherenkov Telescope Array Observatories detectors, the new-generation astronomical observatories, one of which is situated in Chile and the other in the Canary Islands, that will analyze the Universe through extremely high energy gamma rays.