Heavily-Obscured AGNs and the Host Galaxies in the XMM-SERVS Fields

The XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) contains wide X-ray coverage in three fields: XMM-LSS (5.3 deg²), W-CDF-S (4.6 deg²) and ELAIS-S1 (3.2 deg²). The flare-filtered exposure times are 2.7 Ms, 1.8 Ms, and 0.9 Ms, respectively. In these observations, a total number of 11,925 X-ray point sources are reported, and over 87% of them have reliable multi-wavelength counterpart candidates. The substantial number of AGN candidates (≈ 10,200) in the XMM-SERVS provides a large sample to characterize representative AGN populations, including those with heavy obscuration (N_H > 10²⁴ cm^-2), along with their host galaxies. In this work, we extract X-ray spectra and perform spectral analysis to derive AGN characteristics. Using physical torus models (e.g., borus) and a Monte Carlo sampling method, we uncover representative Compton-Thick (CT) AGN candidates with good signal-to-noise ratios. As a result, we find ~70 sources with over 40% likelihood as CT AGNs, and further obtain an increasing CT fraction from low to high redshift. Our CT candidates also tend to show hard X-ray spectral feature and dust obscuration in their SED fits, which may shed a light on the contribution of obscuration to the co-evolution of AGNs and host galaxies.