Prospect for Future MeV Gamma-ray Active Galactic Nuclei Population Studies

TL;DR

This paper assesses the potential of future MeV gamma-ray missions to study active galactic nuclei, focusing on Seyfert galaxies and FSRQs, and their contribution to the cosmic MeV gamma-ray background.

Contribution

It provides updated spectral models and luminosity functions to predict the detectability of Seyferts and FSRQs with upcoming MeV gamma-ray telescopes.

Findings

Detection of several hundred Seyferts requires sensitivity of 10^-12 erg cm^-2 s^-1.

Detection of several hundred FSRQs requires sensitivity of ~4 x 10^-12 erg cm^-2 s^-1.

Current FSRQ models suggest they can explain up to 30% of the MeV background.

Abstract

While the X-ray, GeV gamma-ray, and TeV gamma-ray skies have been extensively studied, the MeV gamma-ray sky is not well investigated after the Imaging Compton Telescope (COMPTEL) scanned the sky about two decades ago. In this paper, we investigate prospects for active galactic nuclei population studies with future MeV gamma-ray missions using recent spectral models and luminosity functions of Seyfert and flat spectrum radio quasars (FSRQs). Both of them are plausible candidates as the origins of the cosmic MeV gamma-ray background. If the cosmic MeV gamma-ray background radiation is dominated by non-thermal emission from Seyferts, the sensitivity of 10^-12 erg cm^-2 s^-1 is required to detect several hundred Seyferts in the entire sky. If FSRQs make up the cosmic MeV gamma-ray background, the sensitivity of ~4 x 10^-12 erg cm^-2 s^-1 is required to detect several hundred FSRQs following the recent FSRQ X-ray luminosity function. However, based on the latest FSRQ gamma-ray luminosity function, with which FSRQs can explain up to ~30% of the MeV background, we can expect several hundred FSRQs even with the sensitivity of 10^-11 erg cm^-2 s^-1 which is almost the same as the sensitivity goal of the next generation MeV telescopes.