9.1. Are the AGNs in GPS Radio Galaxies Obscured?

The lack of a detection of the central engine in X-rays in the GPS sources could be because either (1) the AGNs are intrinsically weak in X-rays or (2) the soft X-rays to which these ROSAT observations are sensitive are obscured by large columns of cool gas surrounding the nuclei. O'Dea et al. (1996b) estimate that intrinsic absorbing columns of a few times 10²² cm^-2 are sufficient to hide X-ray luminosities of between 10⁴³ and 10⁴⁴ ergs s^-1. The existence of a powerful AGN that emits most of its energy in the IR is consistent with the amount of reprocessed luminosity observed in the mid-IR (Heckman et al. 1994) and the evidence for hot dust in the near-IR (de Vries et al. 1998c). ASCA observations are in progress to determine whether there is indeed a luminous hidden nucleus.