# The composite nature of Dust-Obscured Galaxies (DOGs) at z~2-3 in the COSMOS field: II. The AGN fraction

## TL;DR

This study investigates the X-ray properties and AGN fraction in Dust-Obscured Galaxies at redshifts 2-3, revealing a significant presence of obscured AGNs and emphasizing the importance of combined X-ray and far-IR observations.

## Contribution

It provides the first detailed analysis of X-ray detected AGN fractions in DOGs at z~2-3, highlighting the role of obscured AGNs and the effectiveness of multi-wavelength surveys.

## Key findings

- 27% of X-ray detected DOGs are Compton Thick AGN candidates.
- AGN contribution to IR luminosity exceeds 20% in 19 DOGs.
- AGN fraction increases with 24μm flux and surpasses that of the general 24μm population.

## Abstract

We present the X-ray properties of 108 Dust-Obscured Galaxies (DOGs; F$_{24 \mu m}$/F$_{R} >$ 1000) in the COSMOS field, all of which detected in at least three far-infrared bands with the Herschel Observatory. Out of the entire sample, 22 are individually detected in the hard 2-8 keV X-ray band by the Chandra COSMOS Legacy survey, allowing us to classify them as AGN. Of them, 6 (27%) are Compton Thick AGN candidates with column densities N$_{H}$$>$10$^{24}$ cm$^{-2}$ while 15 are moderately obscured AGNs with 10$^{22}$ $<$ N$_{H}$ $<$ 10$^{24}$ cm$^{-2}$. Additionally, we estimate AGN contributions to the IR luminosity (8-1000$\mu$m rest-frame) greater than 20% for 19 DOGs based on SED decomposition using Spitzer/MIPS 24$\mu$m and the five Herschel bands (100-500 $\mu$m). Only 7 of these are detected in X-rays individually. We performed a X-ray stacking analysis for the 86 undetected DOGs. We find that the AGN fraction in DOGs increases with 24$\mu$m flux and that it is higher than that of the general 24$\mu$m population. However, no significant difference is found when considering only X-ray detections. This strongly motivates the combined use of X-ray and far-IR surveys to successfully probe a wider population of AGNs, particularly for the most obscured ones.