Fermi-LAT Observations of Sagittarius A*: Imaging Analysis

Abstract

Sagittarius A* (Sgr A*)—the supermassive black hole (SMBH) in the center of our galaxy—has been observed in most of the electromagnetic spectrum, from radio to X-rays. Diffuse γ -ray emission has been observed around Sgr A* and a γ -ray point source has been detected coinciding with the SMBH’s position, although there is no definitive association between the two. In this work, we have used ∼11 yr of Fermi Large Area Telescope observations of the point source 4FGL J1745.6–2859 and performed a detailed imaging analysis across four energy bands. Our goal is to elucidate the nature of the γ -ray emission at the Galactic Center (GC) and whether it is associated with the SMBH. We find that the centroid of the emission approaches Sgr A*’s location as the energy increases. Assuming that the γ -ray point source is located at the GC, we estimate a luminosity of 2.61 × 10 36 erg s −1 in the 100 MeV to 500 GeV energy range. This is consistent with Sgr A*’s bolometric luminosity. Based on the point source properties, we ruled out several potential candidates for its nature and favor a cosmic-ray origin either from protons, electrons, or both, accelerated by—or in the vicinity of—the SMBH. Our results indicate that the point source at the GC is indeed the γ -ray counterpart of Sgr A* in the GeV range.