Desarrollo de una estrategia de observación de características espectrales en blázares con CTA

Abstract

Gamma rays are the most energetic type of electromagnetic radiation in the Universe, generated by non-thermal mechanisms that take place during the most energetic processes in the cosmos. The gamma-ray sky is dominated by blazars, a subclass of active galactic nucleus (AGN) in which one of its relativistic jets points towards the Earth. The gamma radiation is attenuated in its path to Earth by interacting with the extragalactic background light (EBL) via pair production. This attenuation is more pronounced for sources located at high redhifts and for very energetic gamma rays, producing the absorption and distortion of the gamma ray spectrum specially at very high energies (VHE, E>100 GeV). Therefore, to study the intrinsic spectrum emitted by the source, we must first correct this effect on the observed spectrum. Gamma rays cannot be detected directly from terrestrial observatories, since when they pass through the atmosphere they interact with air molecules producing a cascade of subatomic particles. The way to detect gamma rays from the ground is through the detection of the so-called ’Cherenkov radiation’, which results from the generated electromagnetic cascade. Cherenkov radiation is in the range of blue and ultraviolet light whose peak emission occurs at ∼350 nm. This type of radiation is produced when a charged particle passes through a dielectric medium at speeds exceeding those of light in that medium. This is what happens to the electrons and relativistic positrons in the cascade when they interact with air molecules. Cherenkov telescopes that detect this radiation are known as ’IACTs’ (Imaging Atmospheric Cherenkov Telescopes). The Cherenkov Telescope Array (CTA) is a scientific project which aims at building more than 100 new generation IACTs for the detection of VHE gamma rays. CTA will consist of two large telescope arrays, one in the southern hemisphere (Paranal Observatory, Chile) and one in the northern (Roque de los Muchachos Observatory, La Palma, Spain). Three types of telescopes with different sizes and sensitivities will be distributed: the LSTs (Large Size Telescopes) for the study of low energy gamma rays (30 - 150 GeV), the MSTs (Medium Size Telescopes) for intermediate energy gamma rays (150 GeV - 5 TeV) and the SSTs (Small Size Telescopes) for higher energy gamma rays (1 - 300 TeV). These are the energy ranges where the sensitivity is optimized, but they can actually detect higher and lower energies depending on the telescope.