Measurement of anisotropies in the large-scale diffuse gamma-ray emission

TL;DR

This paper presents the first measurement of the angular power spectrum of large-scale diffuse gamma-ray emission between 1-50 GeV, revealing anisotropies likely due to unresolved point sources.

Contribution

It provides the first empirical measurement of anisotropies in diffuse gamma-ray emission and compares data with models to identify contributions from unresolved sources.

Findings

Angular power exceeds photon noise at multipoles > 100 for 1-10 GeV.

Detected excess anisotropy suggests unresolved point source contribution.

Results highlight differences between observed data and simulated models.

Abstract

We have performed the first measurement of the angular power spectrum in the large-scale diffuse emission at energies from 1-50 GeV. We compared results from data and a simulated model in order to identify significant differences in anisotropy properties. We found angular power above the photon noise level in the data at multipoles greater than ~ 100 for energies 1< E <10 GeV. The excess power in the data suggests a contribution from a point source population not present in the model.