A posteriori anisotropy study of ultra-high energy cosmic rays ( UHECRs ) with the Pierre Auger Observatory ( PAO ) has shown evidence of excess of cosmic ray particles above 55 EeV within 18 ^ { \circ } of the direction of the radio galaxy Centaurus A .
However , the origin of the excess remains elusive .
We simulate the propagation of different species of particles coming from the direction of Centaurus A in the Galactic magnetic fields , and find that only particles of nuclear charge Z \lesssim 10 can avoid being deflected outside of the 18 ^ { \circ } window of Centaurus A .
On the other hand , considering the increasingly heavy composition of UHECRs at the highest energies measured by PAO , a plausible scenario for cosmic rays from the direction of Centaurus A can be found if they consist of intermediate–mass nuclei .
The chemical composition of cosmic rays can be further constrained by lower-energy cosmic rays of the same rigidity .
We find that cosmic ray acceleration in the lobes of Centaurus A is not favored , while acceleration in the stellar winds that are rich in intermediate-mass nuclei , could meet the requirement .
This suggests that the observed excess may originate from cosmic ray accelerators induced by stellar explosions in the star-forming regions of Centaurus A and/or the Centaurus cluster located behind Centaurus A .