Fermi LAT observations of Sagittarius A*: Imaging Analysis

TL;DR

This study uses 11 years of Fermi LAT data to analyze gamma-ray emission near Sagittarius A*, finding it likely originates from cosmic rays associated with the supermassive black hole, and confirming the gamma-ray counterpart of Sgr A* in the GeV range.

Contribution

The paper provides a detailed imaging analysis of gamma-ray emission at the Galactic Center, establishing the association with Sgr A* and suggesting a cosmic ray origin, which is a novel insight.

Findings

Centroid of gamma-ray emission approaches Sgr A* at higher energies.

Estimated gamma-ray luminosity is consistent with Sgr A*'s bolometric luminosity.

Ruled out several potential sources, favoring a cosmic ray origin.

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 gamma-ray emission has been observed around Sgr A* and a gamma-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 years of Fermi Large Area Telescope (LAT) 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 gamma-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 gamma-ray point source is located at the GC, we estimate a luminosity of 2.61E36 erg/s 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 gamma-ray counterpart of Sgr A* in the GeV range.