Investigating Non-Accreting Supermassive Black Holes as Sources of Ultra-High-Energy Cosmic Rays

Over the past decade, giant surface arrays such as the Pierre Auger Observatory and the Telescope Array have detected cosmic rays with energies reaching hundreds of EeV, yet their sources remain unidentified. The detection of a large-scale dipole anisotropy pointing away from the Galactic plane, combined with the attenuation of ultra-high-energy cosmic rays (UHECRs) during propagation, suggests that their origins lie in nearby extragalactic objects. Most source searches have focused on starburst galaxies and radio-loud active galactic nuclei, which are galaxies hosting a supermassive black hole (SMBH) at their core. As a result, Centaurus A has been identified as a promising candidate. Theoretical models suggest that spinning SMBHs threaded by magnetic fields can accelerate charged particles to ultra-high energies. However, it remains unclear how primary cosmic rays, especially heavier ones, can survive and escape their acceleration region. We begin by considering that large-scale magnetic fields can also arise in the absence of intense AGN activity, suggesting that non-accreting SMBHs may also contribute to the UHECR flux, thereby favoring the survival of the heavy component observed at the end of the primary energy spectrum. Using the latest published data from the Pierre Auger Observatory, we perform a correlation analysis between UHECRs above 20 EeV and a catalog of SMBHs with precisely measured masses. We present results for the full catalog and separately assess the contributions from active and non-active populations. Additionally, we conduct a likelihood ratio test to compare the active and non-active hypotheses.