Investigating γ-ray halos around three HAWC bright sources in Fermi-LAT data

Numerous extended sources around Galactic pulsars have shown significant γ-ray emission from GeV to TeV energies, revealing hundreds of TeV energy electrons scattering off of the underlying photon fields through inverse Compton scattering (ICS). HAWC TeV gamma-ray observations of few-degree extended emission around the pulsars Geminga and Monogem, and LAT GeV emission around Geminga, suggest that systems older than 100 kyr have multi-TeV e± propagating beyond the SNR-PWN system into the interstellar medium. Following the discovery of few γ-ray sources by HAWC at energies E> 100 TeV, we investigate the presence of an extended γ-ray emission in Fermi-LAT data around the three brightest sources detected by HAWC up to 100 TeV. We find an extended emission of θ68 = 1.00+0.05 deg around eHWC J1825-134 and θ68 = 0.71 ± 0.10 deg eHWC −0.07 J1907+063. The analysis with ICS templates on Fermi-LAT data point to diffusion coefficient values which are significantly lower than the average Galactic one. When studied along with HAWC data, the γ-ray Fermi-LAT data provide invaluable insight into the very high-energy electron and positron parent populations.