2022 report from the Auger-TA working group on UHECR arrival directions

Abstract

After over 60 years, the powerful engines that accelerate ultra-high-energy cosmic rays (UHECRs) to the formidable energies at which we observe them from Earth remain mysterious. Assuming standard physics, we expect UHECR sources to lie within the local Universe (up to a few hundred~Mpc). The distribution of matter in the local Universe is anisotropic, and we expect this anisotropy to be imprinted on the distribution of UHECR arrival directions. Even though intervening intergalactic and Galactic magnetic fields deflect charged UHECRs and can distort these anisotropies, some amount of information on the distribution of the sources is preserved. In this proceedings contribution, we present the results of the joint Pierre Auger Observatory and Telescope Array searches for (a) the largest-scale anisotropies (the harmonic dipole and quadrupole) and (b) correlations with a sample of nearby starburst galaxies and the 2MRS catalogue tracing stellar mass within~250~Mpc. This analysis updates our previous results with the most recent available data, notably with the addition of 3~years of new Telescope Array data. The main finding is a correlation between the arrival directions of $12.1{\%}_{-3.1\%}^{+4.5\%}$~of UHECRs detected with $E\ge 38$~EeV by~Auger or with~$E\gtrsim 49$~EeV by~TA and the positions of nearby starburst galaxies on a ${15.1\text{deg}}_{-3.0\text{deg}}^{+4.6\text{deg}}$~angular scale, with a $4.7\sigma$~post-trial significance, up from $4.2\sigma$ obtained in our previous study.

proceedings of the 6th International Symposium on Ultra High Energy Cosmic Rays (UHECR2022), 3-7 October 2022, L'Aquila, Italy

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• Arrival Directions of Cosmic Rays above 32 EeV from Phase One of the Pierre Auger Observatory
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Cited by in corpus (7)

• Probing the Dark Dimension with Auger data
• The role of supernovae inside AGN jets in UHECR acceleration
• Revisiting the implications of Liouville's theorem to the anisotropy of cosmic rays
• Non-parametric Bayesian reconstruction of Galactic magnetic fields using Information Field Theory: The inclusion of line-of-sight information in ultra-high energy cosmic ray backtracking
• Modelling cross-correlations of ultra-high-energy cosmic rays and galaxies
• On gamma rays as predictors of UHECR flux in AGNs
• Displacement of ultra-high-energy cosmic ray source images by the intergalactic magnetic field: the cases of Cen A and M83