Obscuration properties of mid-IR selected AGN
  The goal of this work is to study the obscuration properties of mid-infrared
(mid-IR) selected AGN. For that purpose, we use {\it{WISE}} sources in the
Stripe 82-XMM area to identify mid-IR AGN candidates, applying the Assef et al.
criteria. Stripe 82 has optical photometry $\approx$\,2 times deeper than any
single-epoch SDSS region. XMM-Newton observations cover $\sim$26\,deg$^2$.
Applying the aforementioned criteria, 1946 IR AGN are selected. $\sim 78\%$
have SDSS detection, while 1/3 of them is detected in X-rays, at a flux limit
of $\rm \sim 5 \times 10^{-15}\,erg\,s^{-1}\,cm^{-2}$. Our final sample
consists of 507 IR AGN with X-ray detection and optical spectra. Applying a
$\rm r-W2>6$ colour criterion, we find that the fraction of optically red AGN
drops from 43\% for those sources with SDSS detection to $23\%$ for sources
that also have X-ray detection. X-ray spectral fitting reveals 40 ($\sim8\%$)
X-ray absorbed AGN ($\rm N_H>10^{22}~cm^{-2}$). Among the X-ray unabsorbed AGN,
there are 70 red systems. To further investigate the absorption of these
sources, we construct Spectral Energy Distributions (SEDs) for the total IR AGN
sample. SED fitting reveals that $\sim20\%$ of the optically red sources have
such colours because the galaxy emission is a primary component in the optical
part of the SED, even though the AGN emission is not absorbed at these
wavelengths. SED fitting also confirms that $12\%$ of the X-ray unabsorbed, IR
AGN are optically obscured.
