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 N_H≥2.15× 10^{24} 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})× 10^{22} 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 6R_G < R < 12R_G, which may suggest why there may not be any broad Fe line. The Eddington rate of the source is low (λ_Edd = 0.03), which points to an inefficient accretion, possibly due to a truncated disc.