Heavy obscuration in X-ray weak AGNs

TL;DR

This study uses BeppoSAX observations of Seyfert 2 galaxies to demonstrate that heavy obscuration is common in X-ray weak AGNs, supporting the unified model and impacting X-ray background synthesis.

Contribution

It provides new evidence that the average obscuration in type 2 AGNs is higher than previously estimated, using unbiased optical selection.

Findings

All sources detected in X-ray band

Most sources show heavy obscuration with N_H > 10^25 cm^-2

Supports the unified AGN model and suggests higher obscuration levels

Abstract

We present observations in the 0.1-100 keV spectral band of 8 Seyfert 2 galaxies, obtained by means of BeppoSAX. These sources were selected according to their [OIII] optical emission line flux, to avoid biases against obscuration on the pc scale. All sources were detected. All of them are weak X-ray emitters, and most of them are characterized by prominent iron lines at 6.4-7 keV (EW > 500 eV) and by a flat continuum, indicative of heavy obscuration along our line of sight (N_H > 10^25 cm^-2 in most cases). These results 1) provide further evidence in favor of the unified scenario, and 2) indicate that the average obscuration of type 2 AGNs is very likely much higher than deduced by former X-ray surveys. These findings have important implications for the synthesis of the X-ray background.