Rest-frame stacking of 2XMM catalog sources

Properties of the Fe Kα line

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching bei München, Germany
e-mail: chaudhary@mpe.mpg.de
² Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, 85748 Garching bei München, Germany
³ Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822-1839, USA
⁴ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy

Received: 21 April 2011
Accepted: 12 October 2011

Abstract

Aims. The aim of this work is to characterize the average Fe K emission properties of active galactic nuclei (AGNs) in the source rest-frame.

Methods. We selected a sample of 248 AGNs from the 2XMM catalog, covering a wide redshift range 0 < z < 5 and with the EPIC-PN net 2–10 keV rest-frame counts  ≥ 200 and power law photon indices in the range 1.5–2.2. We employed two fully independent rest-frame stacking procedures to compute the mean Fe K profile. The counting statistics for the integrated spectrum is comparable to the one available for the best studied local Seyferts. To identify the artifacts possibly introduced by the stacking procedure, we have carried out simulations.

Results. We report that the average Fe K line profile in our sample is best represented by a combination of a narrow and a broad line. The equivalent widths of the narrow and broad (parametrized with a diskline) components are  ~30 eV and  ~100 eV, respectively. We also discuss the results of more complex fits and the implications of the adopted continuum modeling on the broad line parameters and its detection significance.