Speaker
Description
As a significant fraction of LHAASO gamma-ray sources are still unidentified, part of them could correspond to illuminated (obscured) molecular clouds, thus acting as so called « dark sources ». Indeed, interaction between cosmic rays and dense clouds can generate gamma-rays via p-p collisions and pion decay processes. Clouds could be illuminated by a nearby accelerator of cosmic-rays or by the cosmic-ray sea itself, slightly enhanced locally. This study aims to find correlations between LHASO faint gamma-ray sources and cloud catalogues such as the Miville-Deschenes catalog (2017). In the GeV band, several works partially treated this topic, focusing on a similar sample of cataloged clouds (Peron et al 2021) and on clouds from the Gould Belt, which are very massive and close. At higher energies, Gould Belt clouds have also been explored by LHAASO but can be seen only via stacking techniques because of their extreme extension (Cao et al 2025), while cataloged clouds have received only little attention (Sinha et al 2022). Since the cosmic-ray sea has a much higher flux at GeV than at multi-TeV, significant differences can be expected from the studies on the GeV band. Thus, using early results from faint sources of the LHAASO 2nd catalog, we identify promising regions where clouds spatially overlap with new LHAASO sources and require only a small cosmic-ray excess (<10) to potentially explain the gamma-ray emissions.
