The XMM-Newton view of PG quasars. II. Properties of the Fe K_α line

The properties of the fluorescence Fe Kα emission lines of a sample of 38 quasars (QSOs) observed with XMM-Newton are studied. These objects are included in the optically selected sample from the Palomar-Green (PG) Bright Quasar Survey with an X-ray luminosity 1.3 × 10⁴³ < L_2-10~keV < 5.1 × 10⁴⁵ erg s^-1 and z ≤ 1.72. For each object in the sample, we investigated the presence of both narrow and broad iron lines in detail. A total of 20 out of the 38 QSOs show evidence of an Fe Kα emission line with a narrow profile. The majority of the lines are consistent with an origin in low ionization material, which is likely to be located in the outer parts of the accretion disk, the molecular torus, and/or the Broad Line Region. The average properties of the narrow Fe Kα emission line observed in the sample are similar to those of Seyfert type galaxies as inferred from recent XMM-Newton and Chandra studies. A broad line has been significantly detected in only three objects. Furthermore, we studied the relationship between the equivalent width (EW) of the iron line and the hard band X-ray luminosity for radio quiet quasars. The analysis indicates that no clear correlation between the strength of the line and the hard X-ray luminosity is present, and our results do not show compelling evidence for an anticorrelation between these two quantities, i.e. the so-called X-ray Baldwin effect.