New limit on high Galactic latitude PeV gamma-ray flux from Tibet AS-gamma data

TL;DR

This paper presents a new, more stringent upper limit on high Galactic latitude PeV gamma-ray flux based on Tibet AS-gamma data, refining previous bounds and discussing implications for cosmic ray sources and dark matter.

Contribution

It introduces a significantly improved upper bound on diffuse gamma-ray flux at high Galactic latitudes using Tibet AS-gamma data, surpassing previous experiments.

Findings

New upper bound on gamma-ray flux is up to ten times stronger.

Implications for cosmic ray sources and dark matter decay models.

Constraints on multi-messenger emission mechanisms.

Abstract

Tibet AS-gamma collaboration has recently reported detection of gamma-rays with energies up to Peta-electronvolt from parts of the Galactic plane. We notice that the analysis of gamma-ray flux by the Tibet AS-gamma experiment also implies an upper bound on the diffuse gamma-ray flux from high Galactic latitudes(|b|>20 degrees) in the energy range between 100 TeV and 1 PeV. This bound is up to an order-of-magnitude stronger than previously derived bounds from GRAPES3, KASCADE and CASA-MIA experiments. We discuss the new TibetAS-gamma limit on high Galactic latitude gamma-ray flux in the context of possible mechanisms of multi-messenger (gamma-ray and neutrino) emission from nearby cosmic ray sources, dark matter decays and large scale cosmic ray halo of the Milky Way.