Cosmic Ray Spallation in Radio-Quiet Active Galactic Nuclei: A Case Study of NGC 4051

TL;DR

This paper explores nuclear spallation in radio-quiet Seyfert galaxies, specifically NGC 4051, suggesting cosmic rays can significantly alter element abundances and produce observable spectral lines within short timescales.

Contribution

It presents the first detailed analysis of spallation effects in radio-quiet AGN, linking cosmic ray activity to observable spectral features and rapid chemical enrichment.

Findings

Detection of a strong 5.44 keV line in NGC 4051.

Evidence for Fe spallation leading to Cr enhancement.

Spallation timescales could be as short as a few years.

Abstract

We investigate conditions for and consequences of spallation in radio-quiet Seyfert galaxies. The work is motivated by the recent discovery of significant line emission at 5.44 keV in Suzaku data from NGC 4051. The energy of the new line suggests an identification as Cr I Ka emission, however the line is much stronger than would be expected from material with cosmic abundances, leading to a suggestion of enhancement owing to nuclear spallation of Fe by low energy cosmic rays from the active nucleus. We find that the highest abundance enhancements are likely to take place in gas out of the plane of the accretion disk and that timescales for spallation could be as short as a few years. The suggestion of a strong nuclear flux of cosmic rays in a radio-quiet Seyfert galaxy is of particular interest in light of the recent suggestion from Pierre Auger Observatory data that ultra-high-energy cosmic rays may originate in such sources.