Extension to lower energies of the cosmic-ray energy window at the Pierre Auger Observatory

Cosmic rays are charged subatomic particles of extraterrestrial origin, which incessantly arrive on Earth, and are the main cause of atmospheric radiation. In the past years, physicists have discovered that such particles may have quite a diverse range of energies, and the largest the energy of such a particle, the lowest is our chance of observing it. This feature is encoded in the so-called energy spectrum, which indicates how many cosmic rays arrive per a certain bin in energy. At the lowest energies, cosmic rays come from within our own Milky Way Galaxy, originating for example from supernova explosions. At the highest energies, such cosmic particles are believed to come mainly from outside our Galaxy, but their origin is still unknown. In this energy regime, a cosmic ray entering the atmosphere will generates a shower of millions of other particles, which we can observe by using several techniques.
With the present study we have decreased the low-energy window for ultra-high-energy cosmic-ray research at the Pierre Auger Observatory by the deployment of the AERAlet facility. This facility offers the opportunity of the study in detail the energy region where the transition from Galactic to extra-Galactic origin might occur and it acts as an external trigger for the radio-detection technique of the Observatory.