Centaurus A at Hard X-rays and Soft Gamma-rays

TL;DR

This paper reviews existing measurements of Centaurus A's hard X-ray and soft gamma-ray emission, highlighting the complexity of its emission components and the importance of the MeV energy range in understanding its spectral energy distribution.

Contribution

It provides a comprehensive overview of all current data in the 100 keV to 50 MeV range for Centaurus A, emphasizing the need for improved spatial resolution and sensitivity.

Findings

Multiple emission components contribute to Cen A's MeV emission.

The second maximum in the spectral energy distribution occurs around 1 MeV.

Current data define the state of knowledge but highlight gaps in spatial resolution.

Abstract

Centaurus A, at a distance of less than 4 Mpc, is the nearest radio-loud AGN. Its emission is detected from radio to very-high energy gamma-rays. Despite the fact that Cen A is one of the best studied extragalactic objects the origin of its hard X-ray and soft gamma-ray emission (100 keV < E < 50 MeV) is still uncertain. Observations with high spatial resolution in the adjacent soft X-ray and hard gamma-ray regimes suggest that several distinct components such as a Seyfert-like nucleus, relativistic jets, and even luminous X-ray binaries within Cen A may contribute to the total emission in the MeV regime that has been detected with low spatial resolution. As the Spectral Energy Distribution of Cen A has its second maximum around 1 MeV, this energy range plays an important role in modeling the emission of (this) AGN. As there will be no satellite mission in the near future that will cover this energies with higher spatial resolution and better sensitivity, an overview of all existing hard X-ray and soft gamma-ray measurements of Cen A is presented here defining the present knowledge on Centaurus A in the MeV energy range.