A BIT OF PHYSICS ABOUT BLAZARS

(Essential Preliminary Information).

Blazars. A blazar is a giant elliptical galaxy with a massive rotating black hole at its core. Twin jets of light and elementary particles, one of which is pointing to Earth, are emitted from the poles along the axis of the black hole’s rotation. This blazar TXS 0506+056 is situated in the night sky just off the left shoulder of the constellation Orion and is about 4 billion light years from Earth.

Gamma Rays from Blazars. According to the Fermi Lat Gamma Ray Telescope results, Blazars are the principal sources of high energy gamma rays.

How a gamma ray is produced in a Blazar. Blazar accelerate electrons (e) along their jets. Electrons interact with low energy photons (γ) from the galaxy. In this processes (Inverse Compton) electrons lose energy while the photon becomes an high energy γ.

Neutrinos from a Blazar are signatures of high energy protons. According to what we know about nuclear physics, in the Blazar environment the most likely process to produce neutrino involves protons (p). One possibility starts with the so called photomeson production: a p interacts with a γ giving protons and pions (π). Pions decay in muons (μ) and neutrinos (ν), muons in electrons and neutrinos.

For these reasons :

1. A High Energy neutrino coming from a Blazar is the smoking gun for a proton of at least one order of magnitude higher energy produced by the Blazar.
2. Establishing a connection in time and direction between high energy neutrinos and gamma rays coming from Blazars is the KEY POINT to state that Blazars are SOURCES for High Energy protons that is High energy Cosmic Rays.

The neutrino as a cosmic messenger. The neutrino is the ideal cosmic messenger, since it does not interacts and it is not deviated by magnetic fields, so bringing the most important information: from where it comes from!

On the other hand charged particles (Cosmic rays) interact, thus loosing their energy, and are deviated by magnetic fields. Photons can e absorbed.