The Influence of Magnetic Fields on UHECR Propagation from Virgo A

TL;DR

This study investigates how galactic and extragalactic magnetic fields influence the propagation and observed arrival directions of ultra high energy cosmic rays from Virgo A, highlighting the significance of magnetic deflections in source identification.

Contribution

The paper presents detailed simulations of UHECR deflections considering multiple magnetic field models, revealing the comparable and sometimes dominant role of EGMF in cosmic ray propagation.

Findings

EGMF deflection is comparable to GMF deflection.

EGMF influence causes asymmetry in arrival directions.

Simulation results vary with different GMF models.

Abstract

Active galactic nuclei (AGN) are considered as one of the most appropriate sources of cosmic rays with energy exceeding $\sim 10^{18}$ eV. Virgo A (M87 or NGC 4486) is the second closest to the Milky Way active galaxy. According to existing estimations it can be a prominent source of ultra high energy cosmic rays (UHECR). However not many events have been registered in the sky region near Virgo A, possibly due to magnetic field influence. In the present work we check UHECR events from the recent sets of data (AUGER, Telescope Array etc.) for possibility of their origination in this AGN. We carried out the simulation of UHECR motion from Virgo A taking into account their deflections in galactic (GMF) as well as extragalactic (EGMF) magnetic fields according to the several latest models. The maps of expected UHECR arrival directions were obtained as a result. It has been found the following: 1) UHECR deflection caused by EGMF is comparable with GMF one, moreover the influence of EGMF sometimes is dominating; 2) effect of EGMF demonstrates obvious asymmetry in the final distribution of expected UHECR arrival directions; 3) the results of simulations depend on chosen GMF model and are still open for the discussion.