Dissecting the inner Galaxy with $\gamma$-ray pixel count statistics

TL;DR

This paper combines advanced statistical techniques to analyze Fermi-LAT gamma-ray data, revealing that unresolved point sources and diffuse emission each account for about 10% of the inner Galaxy's gamma-ray flux, suggesting a potential sub-threshold source contribution to the Galactic center excess.

Contribution

It introduces a novel combination of adaptive template fitting and pixel count statistics to reconstruct flux distributions below detection thresholds in gamma-ray data.

Findings

Point sources and diffuse emission each contribute around 10% of the inner Galaxy emission.

Reconstructed flux distribution of sub-threshold point sources.

Evidence for a sub-threshold point-source contribution to the Galactic center excess.

Abstract

We combine adaptive template fitting and pixel count statistics in order to assess the nature of the Galactic center excess in Fermi-LAT data. We reconstruct the flux distribution of point sources well below the Fermi-LAT detection threshold, and measure their radial and longitudinal profiles in the inner Galaxy. We find that all point sources $and$ the bulge-correlated diffuse emission each contributes $\mathcal{O}$(10\%) of the total inner Galaxy emission, and disclose a potential sub-threshold point-source contribution to the Galactic center excess.