A Study of GeV Gamma-ray Emission toward Supernova Remnant G51.26+0.11 and Its Molecular Environment

Abstract

We reanalyze the Fermi-LAT GeV 𝛾-ray emission in the region of supernova remnant (SNR) G51.26+0.11 and investigate its interstellar molecular environment with the CO-line data. At GeV energies, based on 13.2 years of Fermi-LAT data, the extended 𝛾-ray emission observed in this region is resolved into a uniform-disk source ('Src A') with a significance of 19.5𝜎 and a point source (4FGL J1924.3+1628) with a significance of 4.2𝜎 in 0.2-500 GeV. With an angular radius of ∼ 0.17 • , 'Src A' overlaps with SNR G51.26+0.11 significantly in the line of sight. On the other hand, the morphological coincidence between the SNR and the ∼ +54 km s −1 molecular clouds (MCs) together with the asymmetric or broad 12 CO line profiles near the SNR boundary provides evidence for the very likely SNR-MC interaction. The SNR-MC interaction and the H I absorption features indicate that SNR G51.26+0.11 is located at a kinematic distance of 6.2 ± 0.5 kpc. Combined with the results from the multi-wavelength analysis, the 𝛾-ray emission of the SNR ('Src A') can be naturally explained by a hadronic model with a soft power-law proton spectrum of index ∼ 2.25.