# Searching for luminous absorbed sources in the WISE AGN catalogue

## TL;DR

This study identifies rare, luminous obscured AGN by cross-matching WISE IR-selected AGN with X-ray and optical data, revealing a subset with significant X-ray absorption but little optical obscuration, supporting models of AGN evolution.

## Contribution

It provides the first detailed analysis of the X-ray properties of the largest IR-selected AGN sample, uncovering luminous obscured QSOs with outflowing ionized material.

## Key findings

- Seven obscured AGN with high column density identified
- Six show broad CIV absorption lines and are BALQSOs
- No optical obscuration detected despite X-ray absorption

## Abstract

Mid-IR colour selection techniques have proved to be very efficient in finding AGN. This is because the AGN heats the surrounding dust producing warm mid-IR colours. Using the WISE 3.6, 4.5 and 12 $\mu m$ colours, the largest sample of IR selected AGN has already been produced containing 1.4 million AGN over the whole sky. Here, we explore the X-ray properties of this AGN sample by cross-correlating it with the subsample of the 3XMM X-ray catalogue that has available X-ray spectra and at the same time optical spectroscopy from SDSS. Our goal is to find rare luminous obscured AGN. Our final sample contains 65 QSOs with $\rm{log}\,\nu L_\nu \ge 46.2$\,erg\,s$^{-1}$. This IR luminosity cut corresponds to $\rm{log}\,L_X \approx 45$\,erg\,s$^{-1}$, at the median redshift of our sample ($z=2.3$), that lies at the bright end of the X-ray luminosity function at $z>2$. The X-ray spectroscopic analysis reveals seven obscured AGN having a column density $\rm N_H>10^{22} cm^{-2}$. Six of them show evidence for broad [CIV] absorption lines and five are classified as BALQSOs. We fit the optical spectra of our X-ray absorbed sources to estimate the optical reddening. We find that none of these show any obscuration according to the optical continuum. These sources add to the growing evidence for populations of luminous QSOs with evidence for substantial absorption by outflowing ionised material, similar to those expected to be emerging from their absorbing cocoons in the framework of AGN/galaxy co-evolution.