Detection of Gamma-ray emission from W51 region with LHAASO

Abstract

The "𝜋 0 -decay bump" discovered in the gamma-ray spectra of some interacting supernova remnants (SNRs) is regarded as direct evidence for SNR acceleration of cosmic rays (CRs). However, the ability of SNRs to accelerate CRs to sub-PeV or even PeV energies remains a topic of ongoing debate. We report the LHAASO gamma-ray spectrum measurement of W51C, an interacting SNR exhibiting a 𝜋 0 -decay bump. Owing to the unprecedentedly high sensitivity of LHAASO, we extend the gamma-ray spectrum to ≈ 200 TeV, an order of magnitude higher than the prior measurements. The results indicate a cutoff energy of ≈ 400 TeV for the incident proton spectrum, providing strong evidence that SNRs can serve as accelerators for sub-PeV CRs.

ICRC 2023 Rapporteur: Status of the Gamma-ray Astronomy field

“…The usual suspects are Supernova Remnants (SNRs) due to the fact that they provide in the Galaxy enough power to account for all galactic cosmic rays with only a fraction of their total energy budget. Some already known sources for which we had some updates are W51C, measured by LHAASO up to 300 TeV [47] for which still hadronic models (with an energy cut-off at 400 TeV) are favored to explain the emission. Updates on the measurement of another claimed PeVatron SNR G106.3+2.7 (Boomerang) were shown by HAWC [48], MAGIC [49] and also VERITAS [50], showing a spectrum that extends up to 500 TeV (see Fig.…”