Ultra-High Energy Cosmic Rays, Spiral galaxies and Magnetars

TL;DR

This study finds a significant correlation between ultra-high energy cosmic rays detected by Pierre Auger Observatory and spiral galaxies from the HIPASS catalogue, suggesting these galaxies host cosmic ray sources, with magnetars being prime candidates.

Contribution

It introduces a new correlation analysis using an absorption-free galaxy catalogue, providing evidence linking spiral galaxies and potential cosmic ray sources, especially magnetars.

Findings

Significant correlation between UHECRs and HI-rich spiral galaxies.

Magnetars identified as the most plausible sources of UHECRs.

Observed clustering near Cen A and absence near M87.

Abstract

We measure the correlation between the arrival directions of the highest energy cosmic rays detected by the Pierre Auger Observatory with the position of the galaxies in the HI Parkes All Sky Survey (HIPASS) catalogue, weighted for their HI flux and Auger exposure. The use of this absorption-free catalogue, complete also along the galactic plane, allows us to use all the Auger events. The correlation is significant, being 86.2% for the entire sample of HI galaxies, and becoming 99% when considering the richest galaxies in HI content, or 98% with those lying between 40-55. We interpret this result as the evidence that spiral galaxies are the hosts of the producers of UHECR and we briefly discuss classical (i.e energetic and distant) long Gamma Ray Burst (GRBs), short GRBs, as well as newly born or late flaring magnetars as possible sources of the Auger events. With the caveat that these events are still very few, and that the theoretical uncertainties are conspicuous, we found that newly born magnetars are the best candidates. If so, they could also be associated with sub-energetic, spectrally soft, nearby, long GRBs. We finally discuss why there is a clustering of Auger events in the direction on the radio-galaxy Cen A and an absence of events in the direction of the radio-galaxy M87.