Deep Observation of the Giant Radio Lobes of Centaurus A with the Fermi Large Area Telescope

TL;DR

This study uses an expanded Fermi-LAT data set to analyze the high-energy gamma-ray emission from Centaurus A's giant radio lobes, revealing extended emission and detailed spectral characteristics that inform models of particle acceleration.

Contribution

It provides the first detailed spatial and spectral analysis of Centaurus A's lobes with higher statistics, detecting extended gamma-ray emission beyond radio images and reconstructing their spectral energy distribution.

Findings

Detection of gamma-ray emission up to 6 GeV from both lobes.

Evidence of gamma-ray extension beyond radio images in the northern lobe.

Reconstructed spectral energy distribution for the lobes.

Abstract

The detection of high energy (HE) {\gamma}-ray emission up to about 3 GeV from the giant lobes of the radio galaxy Centaurus A has been recently reported by the Fermi-LAT Collaboration based on ten months of all-sky survey observations. A data set more than three times larger is used here to study the morphology and photon spectrum of the lobes with higher statistics. The larger data set results in the detection of HE {\gamma}-ray emission (up to about 6 GeV) from the lobes with a significance of more than 10 and 20 {\sigma} for the North and the South lobe, respectively. Based on a detailed spatial analysis and comparison with the associated radio lobes, we report evidence for a substantial extension of the HE {\gamma}-ray emission beyond the WMAP radio image in the case of the Northern lobe of Cen A. We reconstruct the spectral energy distribution (SED) of the lobes using radio (WMAP) and Fermi-LAT data from the same integration region. The implications are discussed in the context of hadronic and leptonic scenarios.