A Self-Consistent Model of the Ultra High-Energy Gamma-Ray Emission of Pulsar Wind Nebulae: Insights from LHAASO and ATNF Catalogs

TL;DR

This paper develops a self-consistent, data-driven model of ultra-high-energy gamma-ray emission from pulsar wind nebulae, integrating catalogs and statistical methods to better understand their contribution to galactic gamma-ray backgrounds.

Contribution

It introduces a novel self-consistent model that links ATNF and LHAASO catalogs, incorporating censored regression to account for unresolved sources and improve emission estimates.

Findings

Reproduces the number of LHAASO-detected PWNe with specific pulsar misalignment fractions.

Suggests most unidentified LHAASO sources are likely PWNe with unseen pulsars.

Finds unresolved PWNe contribute less than 10-30% to the gamma-ray background.

Abstract

Pulsar wind nebulae (PWNe) are the dominant Ultra-high-energy (UHE) gamma-ray sources in the LHAASO catalog suggesting that they are the dominant leptonic PeVatrons in our Galaxy. Despite this, still very little is known about their UHE gamma-ray emission, their number in the Galaxy, or their contribution to the gamma-ray emission of our Galaxy. In this work, we propose a self-consistent data-driven model of the UHE gamma-ray emission of PWNe based on the ATNF and LHAASO catalogs. More specifically, we build a model of the UHE gamma-ray emission of PWNe that preserves the statistical relationships in the ATNF catalog and reproduces the number of PWNe detected in the LHAASO catalog. To cope with the limited data available in the LHAASO catalog when performing fits on gamma-ray data, we introduce the concept of censored regression that allows to also use the information provided by unresolved sources. Using our model, we find that reproducing the number of PWNe detected by LHAASO requires either fractions of misaligned pulsars smaller ($\lesssim60\%$) than usually found in the literature, or that some of the associations of PWNe to ATNF pulsars made by LHAASO may not be true. In both cases, we find that in order to reach self-consistency between radio and gamma-ray data, it is necessary that the majority of the unidentified sources in the LHAASO catalog are PWNe associated to an unseen pulsar. Moreover, using our model we also find that the contribution of unresolved PWNe to the total (diffuse) gamma-ray background measured by LHAASO in the $1-1000\,\rm{TeV}$ range is always smaller than $\lesssim10\%$ ($\lesssim30\%$). We conclude that PWNe mostly contribute to the source component of the UHE gamma-ray sky, while having almost no imprint on its diffuse component.