XMM-Newton unveils the complex iron K α region of Mrk 279

Abstract

We present the results of a ∼160 ks-long XMM-Newton observation of the Seyfert 1 galaxy Mrk 279. The spectrum shows evidence of both broad and narrow emission features. The FeKα line may be equally well explained by a single broad Gaussian (FWHM ∼ 10 000 km s-1) or by two components: an unresolved core plus a very broad profile (FWHM ∼ 14 000 km s-1). For the first time we quantified, via the "locally optimally emitting cloud" model, the contribution of the broad line region (BLR) to the absolute luminosity of the broad component of the FeKα at 6.4 keV. We find that the contribution of the BLR is only ∼3%. In the two-line component scenario, we also evaluated the contribution of the highly ionized gas component, which produces the Fe xxvi line in the iron K region. This contribution to the narrow core of the FeKa line is marginal <0.1%. Most of the luminosity of the unresolved, component of FeKα may come from the obscuring torus, while the very-broad associated component may come from the accretion disk. However, models of reflection by cold gas are difficult to test because of the limited energy band. The Fe xxvi line at 6.9 keV is consistent to be produced in a high column density (NH ∼ 1023 cm -2), extremely ionized (log ∼ 5.5-7) gas. This gas may be a highly ionized outer layer of the torus. © 2010 ESO.