Correlations between Ultrahigh Energy Cosmic Rays and Infrared-Luminous Galaxies

TL;DR

This study confirms a correlation between ultrahigh energy cosmic rays and infrared-luminous galaxies, suggesting these galaxies are likely sources of UHECRs, based on comprehensive analysis with the PSCz catalog and significance testing.

Contribution

It demonstrates a significant correlation between UHECRs and high IR luminosity galaxies using a complete, volume-limited catalog, strengthening the link between IR galaxies and cosmic ray sources.

Findings

Strong correlation at z < 0.016, psi = 2.1 deg, L_ir > 10^{10.5}L_sun

Correlation stronger than 90% of scrambled luminosity trials

UHECR horizon confirmed independent of VCV catalog biases

Abstract

We confirm the UHECR horizon established by the Pierre Auger Observatory using the heterogeneous Veron-Cetty Veron (VCV) catalog of AGNs, by performing a redshift-angle-IR luminosity scan using PSCz galaxies having infrared luminosity greater than 10^{10}L_sun. The strongest correlation -- for z < 0.016, psi = 2.1 deg, and L_ir > 10^{10.5}L_sun -- arises in fewer than 0.3% of scans with isotropic source directions. When we apply a penalty for using the UHECR energy threshold that was tuned to maximize the correlation with VCV, the significance degrades to 1.1%. Since the PSCz catalog is complete and volume-limited for these parameters, this suggests that the UHECR horizon discovered by the Pierre Auger Observatory is not an artifact of the incompleteness and other idiosyncrasies of the VCV catalog. The strength of the correlation between UHECRs and the nearby highest-IR-luminosity PSCz galaxies is stronger than in about 90% percent of trials with scrambled luminosity assignments for the PSCz galaxies. If confirmed by future data, this result would indicate that the sources of UHECRs are more strongly associated with luminous IR galaxies than with ordinary, lower IR luminosity galaxies.