AEGIS: Radio and Mid-Infrared Selection of Obscured AGN Candidates

TL;DR

This study demonstrates that combining radio and mid-infrared data effectively identifies obscured AGN candidates, many of which are missed by traditional optical or X-ray surveys, thus enhancing the completeness of AGN catalogs.

Contribution

The paper introduces a multi-wavelength selection method using radio and mid-infrared data to identify obscured AGNs that are often missed by other detection techniques.

Findings

Only 30% of candidates are X-ray detected, indicating many are heavily obscured.

Stacked X-ray images show low activity, supporting the obscured AGN hypothesis.

Less than 40% of candidates show traditional AGN signatures, highlighting the method's unique detection capability.

Abstract

The application of multi-wavelength selection techniques is crucial for discovering a complete and unbiased set of Active Galactic Nuclei (AGNs). Here, we select a sample of 72 AGN candidates in the Extended Groth Strip (EGS) using deep radio and mid-infrared data from the Very Large Array (VLA) and the Spitzer Space Telescope, and analyze their properties across other wavelengths. Only 30% of these sources are detected in deep 200 ks Chandra X-ray Observatory pointings. The X-ray detected sources demonstrate moderate obscuration with column densities of N_H > 10^22 cm^-2. A stacked image of sources undetected by Chandra shows low levels of X-ray activity, suggesting they may be faint or obscured AGNs. Less than 40% of our sample are selected as AGNs with optical broad lines, mid-infrared power laws, or X-ray detections. Thus, if our candidates are indeed AGNs, the radio/mid-infrared selection criteria we use provide a powerful tool for identifying sources missed by other surveys.