Note on galaxy catalogues in UHECR flux modelling

TL;DR

This paper examines how different galaxy catalogues affect ultra-high energy cosmic ray flux predictions, demonstrating that predictions are consistent across catalogues and introducing a measure to quantify anisotropies in flux models.

Contribution

It shows that flux predictions based on different galaxy catalogues are consistent and develops a new measure to quantify anisotropies in UHECR flux models.

Findings

Predictions using KKKST and XSCz catalogues agree well.

The new anisotropy measure helps assess the impact of model assumptions.

The KKKST catalogue is suitable for UHECR anisotropy studies.

Abstract

We consider the dependence of ultra-high energy cosmic ray (UHECR) flux predictions on the choice of galaxy catalogue. We demonstrate that model predictions by Koers & Tinyakov (2009b), based on the so-called KKKST catalogue, are in good agreement with predictions based on the XSCz catalogue, a recently compiled catalogue that contains spectroscopic redshifts for a large fraction of galaxies. This agreement refutes the claim by Kashti (2009) that the KKKST catalogue is not suited for studies of UHECR anisotropy due to its dependence on photometric redshift estimates. In order to quantify the effect of galaxy catalogues on flux predictions, we develop a measure of anisotropies associated with model flux maps. This measure offers a general criterion to study the effect of model parameters and assumptions on the predicted strength of UHECR anisotropies.