The XMM-Newton view of PG quasars: II. Properties of the Fe K-alpha line

TL;DR

This study analyzes the properties of Fe K-alpha emission lines in 38 PG quasars observed with XMM-Newton, revealing mostly narrow lines with some broad detections, and finds no clear correlation between line strength and X-ray luminosity.

Contribution

It provides a detailed analysis of Fe K-alpha line profiles in quasars, comparing their properties to Seyfert galaxies and examining the X-ray Baldwin effect.

Findings

20 out of 38 quasars show narrow Fe K-alpha lines.

Broad lines are significantly detected in only three quasars.

No clear correlation between Fe line equivalent width and X-ray luminosity.

Abstract

The properties of the fluorescence Fe K-alpha 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 1.3E43<L(2-10 keV)<5.1E45 ergs/s 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 K-alpha 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 K-alpha 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.