Exploring the population of Galactic very-high-energy $\gamma$-ray sources

TL;DR

This paper models the population of Galactic very-high-energy gamma-ray sources using H.E.S.S. survey data, estimating their numbers and contributions, and explores future constraints with CTA and machine learning techniques.

Contribution

It introduces a numerical population model for Galactic VHE gamma-ray sources that accounts for observational biases and incorporates machine learning for enhanced data analysis.

Findings

Estimated total number of VHE gamma-ray sources in the Galaxy.

Quantified the sources' contribution to diffuse gamma-ray emission.

Assessed CTA's potential to constrain the population model.

Abstract

At very high energies (VHE), the emission of $\gamma$ rays is dominated by discrete sources. Due to the limited resolution and sensitivity of current-generation instruments, only a small fraction of the total Galactic population of VHE $\gamma$-ray sources has been detected significantly. The larger part of the population can be expected to contribute as a diffuse signal alongside emission originating from propagating cosmic rays. Without quantifying the source population, it is not possible to disentangle these two components. Based on the H.E.S.S. Galactic plane survey, a numerical approach has been taken to develop a model of the population of Galactic VHE $\gamma$-ray sources, which is shown to account accurately for the observational bias. We present estimates of the absolute number of sources in the Galactic Plane and their contribution to the total VHE $\gamma$-ray emission for five different spatial source distributions. Prospects for CTA and its ability to constrain the model are discussed. Finally, first results of an extension of our modelling approach using machine learning to extract more information from the available data set are presented.