Investigating the origin of the Fe emission lines of the Seyfert 1 galaxy Mrk 205

Abstract

We have investigated the nature and origin of the Fe K emission lines in Mrk 205 using observations with Suzaku and XMM-Newton, aiming to resolve the ambiguity between a broad emission line and multiple unresolved lines of higher ionization. We detect the presence of a narrow Fe K α emission line along with a broad-band Compton reflection hump at energies E> 10 keV. These are consistent with reflected emission of hard X-ray photons off a Compton-thick material of NH≥ 2.15× 1024 cm-2. In addition we detect a partially covering ionized absorption with ionization parameter log (ξ/ erg cm s-1)=1.9-0.5+0.1, column density N H=(5.6-1.9+2.0)× 1022 cm-2, and a covering factor of 0.22-0.06+0.09. We detect the presence of emission arising out of ionized disc reflection contributing in the soft and hard X-rays consistently in all the observations. We however, could not definitely ascertain the presence of a relativistically broadened Fe line in the X-ray spectra. Using relativistic reflection models, we found that the data are unable to statistically distinguish between the scenarios when the supermassive black hole is non-rotating and when it is maximally spinning. Using the disc reflection model we also find that the accretion disc of the active galactic nucleus may be truncated at a distance 6RG < R < 12RG, which may suggest why there may not be any broad Fe line. The Eddington rate of the source is low (λEdd = 0.03), which points to an inefficient accretion, possibly due to a truncated disc.