Nuclear X-Ray Properties of the Peculiar Radio-loud Hidden AGN 4C+29.30

Abstract

We present results from a study of nuclear emission from a nearby radio galaxy, 4C+29.30, over a broad 0.5-200 keV X-ray band. This study used new XMM-Newton (~17 ks) and Chandra (~300 ks) data, and archival Swift/BAT data from the 58 month catalog. The hard (>2 keV) X-ray spectrum of 4C+29.30 can be decomposed into an intrinsic hard power law (Γ ~ 1.56) modified by a cold absorber with an intrinsic column density N _{H, z} ~ 5 × 10²³ cm^-2, and its reflection (|Ω/2π| ~ 0.3) from a neutral matter including a narrow iron Kα emission line at a rest-frame energy ~6.4 keV. The reflected component is less absorbed than the intrinsic one with an upper limit on the absorbing column of N ^refl _{H, z} < 2.5 × 10²² cm^-2. The X-ray spectrum varied between the XMM-Newton and Chandra observations. We show that a scenario invoking variations of the normalization of the power law is favored over a model with variable intrinsic column density. X-rays in the 0.5-2 keV band are dominated by diffuse emission modeled with a thermal bremsstrahlung component with temperature ~0.7 keV, and contain only a marginal contribution from the scattered power-law component. We hypothesize that 4C+29.30 belongs to a class of "hidden" active galactic nuclei containing a geometrically thick torus. However, unlike the majority of hidden AGNs, 4C+29.30 is radio-loud. Correlations between the scattering fraction and Eddington luminosity ratio, and between black hole mass and stellar velocity dispersion, imply that 4C+29.30 hosts a black hole with ~10⁸ M _⊙ mass.