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We explore the nature of Infrared Excess sources (IRX), which are proposed as candidates for luminous [  L X  (2–10  keV) &gt; 10 43   erg   s −1  ] Compton thick  ( N  H  &gt; 2 × 10 24   cm −2 )  QSOs at   z ≈ 2 . Lower redshift,   z ≈ 1 , analogues of the distant IRX population are identified by first redshifting to   z = 2  the spectral energy distributions (SEDs) of all sources with secure spectroscopic redshifts in the AEGIS (6488) and the GOODS‐North (1784) surveys and then selecting those that qualify as IRX sources at that redshift. A total of 19 galaxies are selected. The mean redshift of the sample is   z ≈ 1 . We do not find strong evidence for Compton thick QSOs in the sample. For nine sources with X‐ray counterparts, the X‐ray spectra are consistent with Compton thin active galactic nucleus (AGN). Only three of them show tentative evidence for Compton thick obscuration. The SEDs of the X‐ray undetected population are consistent with starburst activity. There is no evidence for a hot dust component at the mid‐infrared associated with AGN heated dust. If the X‐ray undetected sources host AGN, an upper limit of   L X  (2–10  keV) = 10 43   erg   s −1   is estimated for their intrinsic luminosity. We propose that a large fraction of the   z ≈ 2  IRX population is not Compton thick quasi‐stellar objects (QSOs) but low‐luminosity [  L X  (2–10  keV) &lt; 10 43   erg   s −1  ], possibly Compton thin, AGN or dusty starbursts. It is shown that the decomposition of the AGN and starburst contribution to the mid‐IR is essential for interpreting the nature of this population, as star formation may dominate this wavelength regime.

Infrared Excess sources: Compton thick QSOs, low‐luminosity Seyferts or starbursts?