Discordant optical and X-ray classification of AGN

TL;DR

This study investigates the mismatch between optical and X-ray classifications of AGN, revealing galaxy dilution as a key factor causing apparent discrepancies in observed properties.

Contribution

It provides a detailed multi-wavelength analysis of two AGN, demonstrating galaxy dilution as the cause of optical/X-ray classification mismatch.

Findings

Galaxy dilution explains optical/X-ray classification mismatch.

One AGN has an intrinsically high Balmer decrement.

The other AGN resides in a more massive galaxy than expected.

Abstract

To provide insight into the apparent mismatch between the optical and X-ray absorption properties observed in 10-30 % of Active Galactic Nuclei (AGN), we have conducted a detailed study of two X-ray unabsorbed AGN with a type-2 optical spectroscopic classification. In addition to high quality X-ray spectroscopic observations, that we used to determine both the AGN luminosities and absorption, we have a VLT/XSHOOTER UV-to-near-IR high resolution spectrum for each object, that we used to determine the AGN intrinsic emision corrected for both contamination from the AGN hosts and extinction. Our analysis has revealed that the apparent mismatch is provoked by galaxy dilution. We dilution of two AGN with extreme properties: one of them has an intrinsically very high Balmer decrement while the other lies in a galaxy more massive than expected.