Attenuation of LHAASO PeVatrons by Interstellar Radiation Field and Cosmic Microwave Background Radiation

TL;DR

This paper quantifies how interstellar radiation and cosmic microwave background attenuate gamma rays from PeVatrons detected by LHAASO, aiding in understanding their true emission spectra and acceleration mechanisms.

Contribution

It provides the first detailed calculations of gamma-ray absorption effects for LHAASO PeVatrons using the galprop model, improving spectral correction accuracy.

Findings

Absorption reaches 30% at 100 TeV for some sources.

Absorption reaches 80% at 3 PeV for certain sources.

Gamma-ray attenuation helps distinguish radiation mechanisms.

Abstract

"PeVatrons" refer to astrophysical sources capable of accelerating particles to energies around $10^{15}$ electron volts and higher, potentially contributing to the cosmic ray spectrum in the knee region. Recently, LHAASO has discovered a large number of PeVatrons, allowing us to investigate in greater depth the contributions of these sources to cosmic rays above the knee region. However, high-energy gamma rays undergo attenuation due to interactions with the interstellar radiation field and cosmic microwave background radiation, requiring corrections to restore the true spectral characteristics at the source. In this study, using interstellar radiation field model extracted from galprop code, we quantitatively calculated the spectral absorption effects of sources listed in the first LHAASO source catalog, with some sources showing absorption reaching 30\% at 100 TeV and 80\% at 3 PeV. We also calculated the high energy gamma ray absorption effects of Galactic microquasars, which are potential PeVatrons. By calculating the absorption effects, it will help differentiate the radiation mechanisms of the acceleration sources.