# The obscured quasar population from optical, mid-infrared, and X-ray surveys

## TL;DR

This paper reviews recent multi-wavelength efforts to identify and understand the population of obscured AGN, especially Type 2 quasars, highlighting current observational challenges and findings.

## Contribution

It provides a comprehensive review of the identification methods and recent results on obscured AGN, emphasizing the optical selection of Type 2 quasars from SDSS.

## Key findings

- Significant number of obscured AGN identified across wavelengths
- Type 2 quasars are key to understanding the obscured AGN population
- Current data still lack a complete census due to observational limitations

## Abstract

Over the last few years, optical, mid-infrared and X-ray surveys have brought to light a significant number of candidate obscured AGN and, among them, many Type 2 quasars, the long-sought after "big cousins'' of local Seyfert 2 galaxies. However, despite the large amount of multi-wavelength data currently available, a proper census and a panchromatic view of the obscured AGN/quasar population are still missing, mainly due to observational limitations. Here we provide a review of recent results on the identification of obscured AGN, focusing primarily on the population of Type 2 quasars selected in the optical band from the Sloan Digital Sky Survey.