An XMM-Newton survey of broad iron lines in Seyfert galaxies

Nandra, K.; O’Neill, Paul M.; George, I. M.; Reeves, J. N.

doi:10.1111/j.1365-2966.2007.12331.x

Cited by 595 publications

(820 citation statements)

References 166 publications

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“…Additionally, the lack of a broad Fe Kα emission line at 6.4 keV in most of the LLAGN studied up until now, originating from a standard disk in typical luminous AGN, might suggest the truncation of this structure at a radius much larger than the innermost stable circular orbit (ISCO) where a radiatively inefficient accretion flow (RIAF) structure forms in the inner part. We note that the last argument, lack of a broad Fe K line, used to point at the existence of a RIAF in LINERs is not decisive since a small fraction, 25−30%, of Seyfert galaxies exhibit broadened emission in the iron K band (Nandra et al 2007).…”

Section: Ngc 4278 Sed Comparison To Other Llagnmentioning

confidence: 99%

X-ray and multiwavelength view of NGC 4278

Younes

Porquet

Sabra

et al. 2010

A&A

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Context. The emission mechanism responsible for the bulk of energy from radio to X-rays in low ionization emission line regions (LINERs) and low luminosity active galactic nuclei (LLAGN) has been long debated. Based on UV to X-ray and radio to UV flux ratios, some argue that LINERs/LLAGN are a scaled-down version of their more luminous predecessors Seyfert galaxies. Others, based on the lack of X-ray short (hours) time-scale variability, the non detection of an iron line at 6.4 keV, and the faint UV emission compared to typical AGNs, suggest the truncation of the classical thin accretion disk in the inner regions of the AGN where a radiatively inefficient accretion flow (RIAF) structure forms. Aims. We investigate the LINER-Seyfert connection by studying the unabsorbed LINER galaxy NGC 4278 that accretes at a low rate (L bol/Edd ∼ 7 × 10 −6 ) but exhibits a broad Hα line, and a point-like nucleus in radio, optical, UV and X-rays. Methods. We analyzed one XMM-Newton and seven Chandra X-ray observations of NGC 4278 spread over a three year period, allowing the study of the X-ray variability at different time-scales (hours, months, years). We also examined the radio to X-ray spectral energy distribution to constrain the accretion mode in the nucleus of NGC 4278. Results. Long time-scale (months) variability is observed where the flux increased by a factor of ∼3 on a time-scale of a few months and by a factor of 5 between the faintest and the brightest observation separated by ∼3 years. During the XMM-Newton observation, where the highest flux level is detected, we found a 10% flux increase on a short time-scale of a few hours, while the light curves for the different Chandra observations do not show short time-scale (minutes to hours) variability. A combination of an absorbed power law (N H ≈ 10 20 cm −2 , Γ = 2.2 +0.1 −0.2 ) plus a thermal component (kT ≈ 0.6 keV) were able to fit the Chandra spectra. The XMM-Newton spectra, where the highest X-ray flux is detected, are well fitted with an absorbed power-law with no need for a thermal component as the emission from the power-law component is dominant. The power-law photon index is ∼2.1 and the hydrogen column density is of the order of 10 20 cm −2 . Neither a narrow nor a broad Fe Kα emission line at 6.4 keV are detected with a 22 eV and 118 eV upper limits derived on their equivalent widths. We derive optical fluxes from archival HST ACS observations and detected optical variability on time-scales of years. For the first time for this source, thanks to the optical/UV monitor on board XMM-Newton, we obtained simultaneous UV and X-ray flux measurements. We constructed SEDs based on simultaneous or quasi simultaneous observations and compared them to LINER, radio-loud, and radio-quiet quasar SEDs. We find that at a low X-ray flux the NGC 4278 SED resembles that of typical LINER sources where the radio to X-ray emission can be considered as originating from a jet and/or RIAF, whereas at a high X-ray flux, NGC 4278 SED is more like a low luminosity Seyfert SED...

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Section: Ngc 4278 Sed Comparison To Other Llagnmentioning

confidence: 99%

X-ray and multiwavelength view of NGC 4278

Younes

Porquet

Sabra

et al. 2010

A&A

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“…We assume the photon index, Γ, is drawn from a Gaussian distribution with a mean of 1.9 and standard deviation of 0.2 (corresponding to the observed distribution of intrinsic photon indices in Xray spectral studies of nearby AGNs, e.g. Nandra et al 2007). We Table 2.…”

Section: Probability Distribution Function For a Single Sourcementioning

confidence: 99%

The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5

Aird

Coil

Georgakakis

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We present new measurements of the evolution of the X-ray luminosity functions (XLFs) of unabsorbed and absorbed Active Galactic Nuclei (AGNs) out to z ∼ 5. We construct samples containing 2957 sources detected at hard (2-7 keV) X-ray energies and 4351 sources detected at soft (0.5-2 keV) energies from a compilation of Chandra surveys supplemented by wide-area surveys from ASCA and ROSAT. We consider the hard and soft X-ray samples separately and find that the XLF based on either (initially neglecting absorption effects) is best described by a new flexible model parametrization where the break luminosity, normalization and faint-end slope all evolve with redshift. We then incorporate absorption effects, separately modelling the evolution of the XLFs of unabsorbed (20 < log N H < 22) and absorbed (22 < log N H < 24) AGNs, seeking a model that can reconcile both the hard-and soft-band samples. We find that the absorbed AGN XLF has a lower break luminosity, a higher normalization, and a steeper faint-end slope than the unabsorbed AGN XLF out to z ∼ 2. Hence, absorbed AGNs dominate at low luminosities, with the absorbed fraction falling rapidly as luminosity increases. Both XLFs undergo strong luminosity evolution which shifts the transition in the absorbed fraction to higher luminosities at higher redshifts. The evolution in the shape of the total XLF is primarily driven by the changing mix of unabsorbed and absorbed populations.

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“…We replaced the Fe Kα emission line in turn with a cold reflection component pexmon (Nandra et al 2007), an ionized reflection component xillver (García et al 2014), and a photoionized emission component photemis (Kallman & Bautista 2001). We assumed an inclination angle of 30°consistent with the radio jet, a standard solar abundance for iron, and a high-energy cutoff of E=150 keV as estimated from hard X-ray observations ).…”

Section: Fe K Emissionmentioning

confidence: 99%

The Complex Circumnuclear Environment of the Broad-Line Radio Galaxy 3c 390.3 Revealed by Chandra Hetg

Tombesi

Reeves

Kallman

et al. 2016

ApJ

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We present the first high spectral resolution X-ray observation of the broad-line radio galaxy 3C390.3 obtained with the high-energy transmission grating spectrometer on board the Chandra X-ray Observatory. The spectrum shows complex emission and absorption features in both the soft X-rays and Fe K band. We detect emission and absorption lines in the energy range E=700-1000 eV associated with ionized Fe L transitions (Fe XVII-XX). An emission line at the energy of E;6.4 keV consistent with the Fe Kα is also observed. Our best-fit model requires at least three different components: (i) a hot emission component likely associated with the hot interstellar medium in this elliptical galaxy with temperature kT=0.5±0.1 keV; (ii) a warm absorber with ionization parameter logξ=2.3±0.5 erg s −1 cm, column density logN H =20.7±0.1 cm −2 , and outflow velocity v out <150 km s −1 ; and (iii) a lowly ionized reflection component in the Fe K band likely associated with the optical broad-line region or the outer accretion disk. These evidences suggest the possibility that we are looking directly down the ionization cone of this active galaxy and that the central X-ray source only photoionizes along the unobscured cone. This is overall consistent with the angle-dependent unified picture of active galactic nuclei.

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An XMM-Newton survey of broad iron lines in Seyfert galaxies

Cited by 595 publications

References 166 publications

X-ray and multiwavelength view of NGC 4278

X-ray and multiwavelength view of NGC 4278

The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5

The Complex Circumnuclear Environment of the Broad-Line Radio Galaxy 3c 390.3 Revealed by Chandra Hetg

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