Ultra-high-energy cosmic rays from low-luminosity active galactic nuclei

Abstract

We investigate the production of ultra-high-energy cosmic ray (UHECR) in relativistic jets from low-luminosity active galactic nuclei (LLAGN). We start by proposing a model for the UHECR contribution from the black holes (BHs) in LLAGN, which present a jet power P j 10 46 erg s −1 . This is in contrast to the opinion that only high-luminosity AGN can accelerate particles to energies 50 EeV. We rewrite the equations which describe the synchrotron selfabsorbed emission of a non-thermal particle distribution to obtain the observed radio flux density from sources with a flat-spectrum core and its relationship to the jet power. We find that the UHECR flux is dependent on the observed radio flux density, the distance to the AGN, and the BH mass, where the particle acceleration regions can be sustained by the magnetic energy extraction from the BH at the center of the AGN. We use a complete sample of 29 radio sources with a total flux density at 5 GHz greater than 0.5 Jy to make predictions for the maximum particle energy, luminosity, and flux of the UHECRs from nearby AGN. These predictions are then used in a semi-analytical code developed in Mathematica (SAM code) as inputs for the Monte-Carlo simulations to obtain the distribution of the arrival direction at the Earth and the energy spectrum of the UHECRs, taking into account their deflection in the intergalactic magnetic fields. For comparison, we also use the CRPropa code with the same initial conditions as for the SAM code. Importantly, to calculate the energy spectrum we also include the weighting of the UHECR flux per each UHECR source. Next, we compare the energy spectrum of the UHECRs with that obtained by the Pierre Auger Observatory.

Ultra high energy cosmic rays and possible signature of black strings

“…The calculated values of η U L pr varies from 0.12 (0.13) to 0.69 (0.73) with average 0.36 (0.43) and standard deviation 0.18 (0.18) for the Kerr (Kerr brane) cases. These values, despite being only upper limits are compatible to the estimatives done in reference [32,35].…”

“…References [33,34] suggests that η X−ray ∼ 10 −5 . A recent publication [35] has investigated the acceleration of UHECRs in low-luminosity AGNs suggesting that η CR ∼ 1/3. However the role of UHECR in the energy balance of the accretion mechanism is yet to be carefully studied.…”

Open Questions in Cosmic-Ray Research at Ultrahigh Energies

“…In addition, radio-quiet, low-luminosity AGN and quasar outflows have been discussed as possible sources of UHECRs (Pe'er et al, 2009;Duan and Caramete, 2015;Wang and Loeb, 2017). These are less powerful individually than jetted AGN but significantly more numerous.…”

LOFAR observations of X-ray cavity systems

“…Additionally, another complication with the lower X-ray luminosity systems is that one cannot assume that any undetected X-ray cavities are well traced by the radio lobes, since such systems often host high-power radio sources whose lobes extend far beyond the dense atmospheres (e.g. NGC 4261, IC4296, IC1459, NGC 1600, NGC 5090, UGC11294, ARP308; Diehl & Statler 2008;Sun 2009;Cavagnolo et al 2010;Duţan & Caramete 2015;Kolokythas et al 2018;Ruffa et al 2019;Grossová et al 2019). Table 3 shows that H α filaments are mostly found in groups and ellipticals where the radio emission is filling the X-ray cavities (the exceptions are NGC 499, NGC 410, and NGC 4104, see Table 3).…”