Dependence of the broad Fe K$\alpha$ line on the physical parameters of AGN

Abstract

In this paper, the dependence of the broad Fe K$\alpha$ line on the physical parameters of AGN, such as the black hole mass $M_{BH}$, accretion rate (equivalently represented by Eddington ratio ${\lambda }_{Edd}$), and optical classification, is investigated by applying the X-ray spectra stacking method to a large sample of AGN which have well measured optical parameters. A broad line feature is detected ($>3\sigma$) in the stacked spectra of the high ${\lambda }_{Edd}$ sub-sample ($\log {\lambda }_{Edd}>-0.9$). The profile of the broad line can be well fitted with relativistic broad line model, with the line energy consistent with highly ionized Fe K$\alpha$ line (i.e. Fe xxvi). A model consisting of multiple narrow lines cannot be ruled out, however. We found hints that the Fe K line becomes broader as the ${\lambda }_{Edd}$ increases. No broad line feature is shown in the sub-sample of broad-line Seyfert 1 (BLS1) galaxies and in the full sample, while a broad line might be present, though at low significance, in the sub-sample of narrow-line Seyfert 1 (NLS1) galaxies. We find no strong dependence of the broad line on black hole masses. Our results indicate that the detection/properties of the broad Fe K$\alpha$ line may strongly depend on ${\lambda }_{Edd}$, which can be explained if the ionization state and/or truncation radius of the accretion disc changes with ${\lambda }_{Edd}$. The non-detection of the broad line in the BLS1 sub-sample can be explained if the the average EW of the relativistic Fe K$\alpha$ line is weak or/and the fraction of sources with relativistic Fe K$\alpha$ line is small in BLS1 galaxies.

12 pages, 9 figures, Published in MNRAS

References in corpus (16)

• Modelling the behaviour of accretion flows in X-ray binaries
• An XMM-Newton survey of broad iron lines in Seyfert galaxies
• Constraining Black Hole Spin Via X-ray Spectroscopy
• Relativistic X-ray Lines from the Inner Accretion Disks Around Black Holes
• A New Sample of Low-mass Black Holes in Active Galaxies
• A Comprehensive Study of 2 000 Narrow Line Seyfert 1 Galaxies from the Sloan Digital Sky Survey: I. The Sample
• The Hard X-ray Spectral Slope as an Accretion-Rate Indicator in Radio-Quiet Active Galactic Nuclei
• Broad-line Balmer Decrements in Blue Active Galactic Nuclei
• On the Iwasawa-Taniguchi effect of radio-quiet AGN
• Radiation pressure and absorption in AGN: results from a complete unbiased sample from Swift
• A compendium of AGN inclinations with corresponding UV/optical continuum polarization measurements
• Average Fe K-alpha emission from distant AGN
• A comparison of hard X-ray photon indices and iron \ka emission lines in X-ray luminous narrow- and broad-line Seyfert 1 galaxies
• Relativistic Fe K$\alpha$ Line Revealed in the Composite X-ray Spectrum of Narrow Line Seyfert 1 Galaxies --- do their black holes have averagely low or intermediate spins?
• Relativistic reflection in the average X-ray spectrum of AGN in the Véron-Cetty & Véron catalogue
• Relativistic iron K alpha line detection in the Suzaku spectra of IC 4329A

Cited by in corpus (7)

• Examining the Physical Conditions of a Warm Corona in Active Galactic Nuclei Accretion Discs
• Relativistic accretion disk reflection in AGN X-ray spectra at z=0.5--4: a study of four \textit{Chandra} deep fields
• Interaction of the accretion flows in corona and disk near the black hole in AGN
• Ionised Accretion Discs in Active Galactic Nuclei: The Effects of a Lamppost with a Variable Height
• A Suzaku sample of unabsorbed narrow-line and broad-line Seyfert 1 galaxies: II. Iron emission and absorption
• A Systematic Study of the Short-Term X-ray Variability of Seyfert Galaxies I. Diversity of the X-ray Rms Spectra
• Strong X-ray Variability of I Zwicky 1: Obscuration from Clumpy Accretion-Disk Winds