Anisotropies, large and small

TL;DR

This paper advances the understanding of ultra-high-energy cosmic ray anisotropies by incorporating detailed composition evolution, source distribution biases, and magnetic deflections, providing new constraints on source densities.

Contribution

It introduces a comprehensive, self-consistent model of UHECR propagation that accounts for composition changes, source bias, and anisotropy generation, improving upon previous simplified approaches.

Findings

Derived limits on UHECR source density consistent with observed anisotropies.

Explored the impact of source distribution bias on anisotropy signals.

Compared anisotropy predictions for dark matter-following and homogeneous source models.

Abstract

We report on several new results using anisotropies of UHECRs. We improve and extend the work of Ding, Globus and Farrar, who modeled the UHECR dipole assuming sources follow the dark matter distribution, accounting for deflections in the Galactic and extragalactic magnetic fields but using a simplified treatment of interactions during propagation. The work presented here employs an accurate and self-consistent treatment of the evolution of composition during propagation, allows for and explores the impact of "bias" in the relation between UHECR sources and the dark matter distribution, and investigates the possible generation of arrival-direction-dependent composition anisotropies. Limits on the source number density consistent with the observed anisotropies are derived for the case where UHECR sources follow the dark matter distribution, and compared to a homogeneous source distribution case.