FR-0 jetted active galaxies: extending the zoo of candidate sites for UHECR acceleration
| Autor: | Paolo Da Vela, Serguei Vorobiov, Jon Paul Lundquist, Chiara Righi, Margot Boughelilba, A. Reimer, Giacomo Bonnoli, Fabrizio Tavecchio, Lukas Merten |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Physics
High Energy Astrophysical Phenomena (astro-ph.HE) Active galactic nucleus Radio galaxy Astrophysics::High Energy Astrophysical Phenomena FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Galaxy Acceleration Lorentz factor symbols.namesake Pair production symbols Spectral energy distribution Astrophysics - High Energy Astrophysical Phenomena Fermi Gamma-ray Space Telescope |
| Popis: | Fanaroff-Riley (FR) 0 radio galaxies form a low-luminosity extension to the well-established ultra-high-energy cosmic-ray (UHECR) candidate accelerators FR-1 and FR-2 galaxies. Their much higher number density -- up to a factor five times more numerous than FR-1 with $z\leq 0.05$ -- makes them good candidate sources for an isotropic contribution to the observed UHECR flux. Here, the acceleration and survival of UHECR in prevailing conditions of the FR-0 environment are discussed. First, an average spectral energy distribution (SED) is compiled based on the \textit{FR0CAT}. These photon fields, composed of a jet and a host galaxy component, form a minimal target photon field for the UHECR, which will suffer from electromagnetic pair production, photo-disintegration, photo-meson production losses, and synchrotron radiation. The two most promising acceleration scenarios based on Fermi-I order and gradual shear acceleration are discussed as well as different escape scenarios. When an efficient acceleration mechanism precedes gradual shear acceleration, e.g., Fermi-I or others, FR-0 galaxies are likely UHECR accelerators. Gradual shear acceleration requires a jet Lorentz factor of $\Gamma>1.6$, to be faster than the corresponding escape. In less optimistic models, a contribution to the cosmic-ray flux between the knee and ankle is expected to be relatively independent of the realized turbulence and acceleration. Comment: 8 pages, 4 figures, 2 tables, ICRC 2021 |
| Databáze: | OpenAIRE |
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