Diffuse Gamma-ray Emission Around 4FGL J1626.0-4917

TL;DR

This study analyzes 17 years of Fermi LAT and Chandra data to reveal extended gamma-ray emission around the unassociated source 4FGL J1626.0-4917, suggesting possible hadronic interactions with surrounding gas.

Contribution

First detailed analysis of extended gamma-ray emission around 4FGL J1626.0-4917 using multi-wavelength data, exploring its origin and potential counterparts.

Findings

Extended gamma-ray emission modeled by a Gaussian disk of 0.28° radius with 7.2 sigma significance.

Gamma-ray spectrum has a photon index of 2.73.

Potential hadronic origin from proton interactions with surrounding gas, with a point X-ray source detected inside.

Abstract

Extended gamma-ray sources provide significant information about particle propagation. 4FGL J1626.0-4917 was labeled as an unassociated source in 4FGL catalog without known counterparts at other wavelengths. We report an analysis on 4FGL J1626.0-4917 with 17 years Fermi Large Area Telescope data and archival Chandra X-ray Observatory data. We find extended GeV emission around this source, which can be modelled by a Gaussian disk of 0.28 degree radius with a significance of the extension of 7.2 sigma. The gamma-ray spectrum of 4FGL J1626.0-4917 has a photon index of 2.73. The gas content, including molecular, neutral and ionized gas, was investigated and the potential hadronic origin is discussed. The diffuse GeV gamma-ray emission may likely originate from the interaction between accelerated protons in 4FGL J1626.0-4917 and the target proton in surrounding gas, although the leptonic process cannot be ruled out. The X-ray spectral analysis was performed, which reveal a point source inside 4FGL J1626.0-4917. We investigate potential counterparts, including the stellar cluster NGC 6134 and the supernova remnant G335.2+0.1. Our results highlight the complexity of unidentified extended gamma-ray sources and the need for further observations.