X-ray studies of quasars with the Einstein Observatory. II

Zamorani, G.; Henry, J. P.; Maccacaro, T.; Tananbaum, H.; Sołtan, A.; Avni, Y.; Liebert, James; Stocke, John T.; Strittmatter, P. A.; Weymann, R. J.; Smith, M.; Condon, J. J.

doi:10.1086/158815

Cited by 375 publications

(280 citation statements)

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“…It is well known (e.g., Zamorani et al 1981) that there is a strong correlation between the nuclear UV magnitudes and the X-ray fluxes for broad-line AGNs. We can see this correlation for the broad-line AGNs in our sample in Figure 30.…”

Section: Failure Of the Simple Unified Modelmentioning

confidence: 99%

The Cosmic Evolution of Hard X-Ray-selected Active Galactic Nuclei

et al. 2005

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We use highly spectroscopically complete deep and wide-area Chandra surveys to determine the cosmic evolution of hard X-ray-selected active galactic nuclei (AGNs). For the deep fields, we supplement the spectroscopic redshifts with photometric redshifts to assess where the unidentified sources are likely to lie. We find that the median redshifts are fairly constant with X-ray flux at z $ 1.We classify the optical spectra and measure the FWHM line widths. Most of the broad-line AGNs show essentially no visible absorption in X-rays, whereas the sources without broad lines (FWHM < 2000 km s À1 ; ''optically narrow'' AGNs) show a wide range of absorbing column densities. We determine hard X-ray luminosity functions for all spectral types with L X ! 10 42 ergs s À1 and for broad-line AGNs alone. At z < 1:2, both are well described by pure luminosity evolution, with L * evolving as (1 þ z) 3:2AE0:8 for all spectral types and as (1 þ z) 3:0AE1:0 for broad-line AGNs alone. Thus, all AGNs drop in luminosity by almost an order of magnitude over this redshift range. We show that this observed drop is due to AGN downsizing rather than to an evolution in the accretion rates onto the supermassive black holes.We directly compare our broad-line AGN hard X-ray luminosity functions with the optical QSO luminosity functions and find that at the bright end they agree extremely well at all redshifts. However, the optical QSO luminosity functions do not probe faint enough to see the downturn in the broad-line AGN hard X-ray luminosity functions and even appear to be missing some sources at the lowest luminosities they probe.We find that broad-line AGNs dominate the number densities at the higher X-ray luminosities, while optically narrow AGNs dominate at the lower X-ray luminosities. We rule out galaxy dilution as a partial explanation for this effect by measuring the nuclear UV/optical properties of the Chandra sources using the Hubble Space Telescope Advanced Camera for Surveys GOODS-North data. The UV/optical nuclei of the optically narrow AGNs are much weaker than expected if the optically narrow AGNs were similar to the broad-line AGNs. We therefore postulate the need for a luminosity-dependent unified model. An alternative possibility is that the broad-line AGNs and the optically narrow AGNs are intrinsically different source populations. We cover both interpretations by constructing composite spectral energy distributions-including long-wavelength data from the mid-infrared to the submillimeterby spectral type and by X-ray luminosity. We use these spectral energy distributions to infer the bolometric corrections (from hard X-ray luminosities to bolometric luminosities) needed to map the accretion history.We determine the accreted supermassive black hole mass density for all spectral types and for broad-line AGNs alone, using the observed evolution of the hard X-ray energy density production rate and our inferred bolometric corrections. We find that only about one-half to one-quarter of the supermassive black hole mass ...

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Section: Failure Of the Simple Unified Modelmentioning

confidence: 99%

The Cosmic Evolution of Hard X-Ray-selected Active Galactic Nuclei

et al. 2005

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“…It is well known that radio-loud AGN have an enhanced X-ray emission mechanism linked to the jets, which can provide an increment in the X-ray emission with respect to radio-quiet AGN with similar optical luminosities (e.g., Zamorani et al 1981;Wilkes & Elvis 1987;Cappi et al 1997). We exclude RL AGN from the total sample using the "standard" definition of radio-loudness, R ≥ 10 ( Kellermann et al 1989) 4 .…”

Section: Type 1 Agn Samplementioning

confidence: 99%

The X-ray to optical-UV luminosity ratio of X-ray selected type 1 AGN in XMM-COSMOS

Lusso

Comastri

Vignali

et al. 2010

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372

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We present a study of the X-ray to optical properties of a sample of 545 X-ray selected type 1 AGN, from the XMM-COSMOS survey, over a wide range of redshifts (0.04 < z < 4.25) and X-ray luminosities (40.6 ≤ Log L [2−10] keV ≤ 45.3). About 60% of them are spectroscopically identified type 1 AGN, while the others have a reliable photometric redshift and are classified as type 1 AGN on the basis of their multi-band Spectral Energy Distributions. We discuss the relationship between UV and X-ray luminosity, as parameterized by the α ox spectral slope, and its dependence on redshift and luminosity. We compare our findings with previous investigations of optically selected broad-line AGN (mostly from SDSS). A highly significant correlation between α ox and L 2500 Å is found, in agreement with previous investigations of optically selected samples. We calculate bolometric corrections, k bol , for the whole sample using hard X-ray luminosities (L [2−10] keV ), and the Eddington ratios for a subsample of 150 objects for which black hole mass estimates are available. We confirm the trend of increasing bolometric correction with increasing Eddington ratio as proposed in previous works. A tight correlation is found between α ox and k bol , which can be used to estimate accurate bolometric corrections using only optical and X-ray data. We find a significant correlation between α ox and Eddington ratio, in which the ratio between X-ray and optical flux decreases with increasing Eddington ratio.

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“…Following Ueda et al (2003), the reflection component is generated with the pexrav model (Magdziarz & Zdziarski 1995) in the XSPEC package with a reflection solid angle of 2π, inclination angle of cos i = 0.5 and solar abundances. We then rescale the X-ray spectrum to a given αox (Zamorani et al 1981) which is defined as…”

Section: The Bolometric Correctionsmentioning

confidence: 99%

Local Supermassive Black Holes, Relics of Active Galactic Nuclei and the X-ray background

Marconi

Risaliti

Gilli

et al. 2005

Growing Black Holes: Accretion in a Cosmological Context

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We quantify the importance of mass accretion during AGN phases in the growth of supermassive black holes (BH) by comparing the mass function of black holes in the local universe with that expected from AGN relics, which are black holes grown entirely with mass accretion during AGN phases. The local BH mass function (BHMF) is estimated by applying the well-known correlations between BH mass, bulge luminosity and stellar velocity dispersion to galaxy luminosity and velocity functions. We find that different correlations provide the same BHMF only if they have the same intrinsic dispersion. The density of supermassive black holes in the local universe which we estimate is ρ BH = 4.6 +1.9 −1.4 h 2 0.7 × 10 5 M ⊙ Mpc −3 . The relic BHMF is derived from the continuity equation with the only assumption that AGN activity is due to accretion onto massive BH's and that merging is not important. We find that the relic BHMF at z = 0 is generated mainly at z < 3 where the major part of BH's growth takes place. Moreover, the BH growth is anti-hierarchical in the sense that smaller BH's (M BH < 10 7 M ⊙ ) grow at lower redshifts (z < 1) with respect to more massive one's (z ∼ 1 − 3). Unlike previous work, we find that the BHMF of AGN relics is perfectly consistent with the local BHMF indicating the local black holes were mainly grown during AGN activity. This agreement is obtained while satisfying, at the same time, the constraints imposed from the X-ray background. The comparison between the local and relic BHMF's also suggests that the merging process is not important in shaping the relic BHMF, at least at low redshifts (z < 3), and allows us to estimate the average radiative efficiency (ε), the ratio between emitted and Eddington luminosity (λ) and the average lifetime of active BH's. Our analysis thus suggests the following scenario: local black holes grew during AGN phases in which accreting matter was converted into radiation with efficiencies ε = 0.04 − 0.16 and emitted at a fraction λ = 0.1 − 1.7 of the Eddington luminosity. The average total lifetime of these active phases ranges from ≃ 4.5 × 10 8 yr for M BH < 10 8 M ⊙ to ≃ 1.5 × 10 8 yr for M BH > 10 9 M ⊙ but can become as large as ∼ 10 9 yr for the lowest acceptable ǫ and λ values.

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X-ray studies of quasars with the Einstein Observatory. II

Cited by 375 publications

References 0 publications

The Cosmic Evolution of Hard X-Ray-selected Active Galactic Nuclei

The Cosmic Evolution of Hard X-Ray-selected Active Galactic Nuclei

The X-ray to optical-UV luminosity ratio of X-ray selected type 1 AGN in XMM-COSMOS

Local Supermassive Black Holes, Relics of Active Galactic Nuclei and the X-ray background

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