Is there a population of unidentified gamma-ray sources distributed along the super-galactic plane?

TL;DR

This study investigates whether unidentified high-energy gamma-ray sources are unevenly distributed along the super-galactic plane, suggesting potential extragalactic origins, with statistical evidence indicating inhomogeneity in their sky distribution.

Contribution

It provides the first statistical analysis of the spatial distribution of unidentified gamma-ray sources around the super-galactic plane, revealing possible extragalactic source populations.

Findings

Inhomogeneous distribution of sources along the super-galactic plane at 95% confidence

Homogeneous distribution around the Galactic plane can be excluded at 90% confidence

Implications discussed for the nature of the source populations

Abstract

The distribution on the sky of unidentified sources at the highest energies where such a population is evident is investigated. For this purpose, sources without identification in the first Fermi-LAT catalog >10 GeV (1FHL) that are good candidates for detection above the 50-100 GeV regime are selected. The distributions of these objects around the Galactic and super-galactic plane are explored. By using a Kolmogorov-Smirnov test it is examined if these sources are distributed homogeneously around these planes. Surprisingly, an indication for an inhomogeneous distribution is found for the case of the super-galactic plane where a homogeneous distribution can be excluded by a confidence level of 95%. On a 90% confidence level also a homogeneous distribution of sources around the Galactic plane can be excluded. For the hypothesis that this reflects the true distribution of sources rather than a statistical fluctuation, implications for the underlying source populations are discussed.