Ultra-high Energy Gamma-rays from Past Explosions in our Galaxy

Abstract

The discovery of the sources of ultra-high energy photons by High-Altitude Water Cerenkov Gamma ray Observatory and Large High Altitude Air Shower Observatory in our Galaxy has revolutionised the field of gamma ray astronomy in the last few years. These emissions are sometimes found in the vicinity of powerful pulsars or supernova remnants associated with giant molecular clouds. Inverse Compton emission by shock accelerated electrons emitted by pulsars and proton-proton interactions of shock accelerated protons emitted by supernova remnants with cold protons in molecular clouds are often identified as the causes of these emissions. In this paper we have selected two ultra-high energy photon sources LHAASO J2108+5157 and LHAASO J0341+5258 which are associated with giant molecular clouds, but no powerful pulsar or supernova remnant has been detected in their vicinity.We have proposed a scenario where shock accelerated electrons and protons are injected in the local environment of these sources from past explosions, which happened thousands of years ago. We show that the observed ultra-high energy photon flux can be explained with the secondary gamma rays produced by the time evolved relativistic electron and proton spectra.

8 pages 5 figures, Accepted in ApJ

References in corpus (4)

• Physical properties of molecular clouds for the entire Milky Way disk
• Parametrization of gamma-ray production cross-sections for pp interactions in a broad proton energy range from the kinematic threshold to PeV energies
• The Milky Way Imaging Scroll Painting (MWISP): Project Details and Initial Results from the Galactic Longitude of 25.8deg to 49.7deg
• A radiation transfer model for the Milky-Way: I. Radiation fields and application to High Energy Astrophysics

Cited by in corpus (4)

• The LHAASO PeVatron bright sky: what we learned
• Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
• Supernova connection of unidentified ultra high energy gamma-ray source LHAASO J2108+5157
• Probing LHAASO Galactic PeVatrons through gamma-ray and neutrino correspondence