The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei
By O. Shemmer, W. N. Brandt, H. Netzer, R. Maiolino, Shai Kaspi Psu, U. TelAviv, I. -. Roma, Technion. 2008
205 citations recorded by the source corpus.
We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3–3.2, including new XMM-Newton observations of four of these sources. We find a significant correlation between the normalized accretion rate (L/LEdd) and the hard X-ray photon index (Γ) for 35 moderate- to high-luminosity RQ AGNs, including our 10 highly luminous sources. Within the limits of our sample, we show that a measurement of Γ and LX can provide an estimate of L/LEdd and black hole mass (MBH) with a mean uncertainty of a factor of ≲3 on the predicted values of these properties. This may provide a useful probe for tracing the history of BH growth in the universe, utilizing samples of X-ray-selected AGNs for which L/LEdd and MBH have not yet been determined systematically. It may prove to be a useful way to probe BH growth in distant Compton-thin type 2 AGNs. We also find that the optical-X-ray spectral slope (αox) depends primarily on optical-UV luminosity rather than on L/LEdd in a sample of RQ AGNs spanning 5 orders of magnitude in luminosity and over 2 orders of magnitude in L/LEdd. We detect a significant Compton-reflection continuum in two of our highly luminous sources, and in the stacked X-ray spectrum of seven other sources with similar luminosities, we obtain a mean relative Compton reflection of R = 0.9+ 0.6−0.5 and an upper limit on the rest-frame equivalent width of a neutral Fe Kα line of 105 eV. We do not detect a significant steepening of the X-ray power-law spectrum below rest-frame 2 keV in any of our highly luminous sources, suggesting that a soft-excess feature, commonly observed in local AGNs, either does not depend strongly on L/LEdd, or is not accessible at high redshifts using current X-ray detectors.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/8d3703008cbaf1f6bf7b6cb76801a819275df001
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Citations in the corpus
- Cosmic X-ray surveys of distant active galaxies (2015, methodology): “In fact, it can be utilized to serve as another SMBH mass-estimation technique via the dependence of LEdd on SMBH mass (e.g., Shemmer et al 2008).”
- CAIXA: a catalogue of AGN in the XMM-Newton archive - II. Multiwavelength correlations (2009, background): “On the other hand, the correlation with the Eddington ratio found by Shemmer et al. (2008) is more significant than our threshold, but only when high-z and high-luminosity quasars are taken into account.”
- A physical model of the broad-band continuum of AGN and its implications for the UV/X relation and optical variability (2018, background): “…by a decrease in Rcorona/Rg (where Rg = GM/c2) correlated with a increase in the hot Comptonisation power law spectra index as Lbol/LEdd increases (Jin et al. 2012a,b; Ezhikode et al. 2017; see also Shemmer et al. 2006, 2008 and Vasudevan & Fabian 2007, 2009 for the hard X-ray spectral index).”
- THE SIMULTANEOUS OPTICAL-TO-X-RAY SPECTRAL ENERGY DISTRIBUTION OF SOFT X-RAY SELECTED ACTIVE GALACTIC NUCLEI OBSERVED BY SWIFT (2010, methodology): “This correlation is similar to those found previously by Grupe (2004) and Shemmer et al. (2008) who reported strong correlations between the Eddington ratio L/LEdd and 11Note that this result may be an artifact of assuming a single power law to fit the whole X-ray spectrum.”
- Simultaneous X-ray/optical/UV snapshots of active galactic nuclei from XMM–Newton: spectral energy distributions for the reverberation mapped sample (2008, result): “However, they also propose a dependence of bolometric correction on Eddington ratio (λEdd = Lbol/LEdd, where LEdd = 1.38× 1038(MBH/MJ) for a black hole of mass MBH), which may now be reinforced by some studies (Kelly et al. 2008, Shemmer et al. 2008).”