On the Faint End of the High‐Redshift Active Galactic Nucleus Luminosity Function

Shankar, Francesco; Mathur, S.

doi:10.1086/512845

Cited by 51 publications

(84 citation statements)

References 68 publications

(105 reference statements)

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“…This confirms that the slope of the faint end of the z > 5.8 AGN luminosity function is significantly flatter than the bright end slope (see e.g. Shankar & Mathur 2007). We also note that the other claimed z > 7 AGN in the CDFS (L306, M 70437) has a 0.5-2 keV flux below our threshold for Chandra-GOODS-MUSIC sources, and its photometric solution for GOODS-MUSIC is broader than that of Luo et al (2010), with a lower limit at z = 2.7.…”

Section: Discussionsupporting

confidence: 77%

Faint high-redshift AGN in theChandradeep field south: the evolution of the AGN luminosity function and black hole demography

Fiore

Puccetti²,

Grazian

et al. 2011

A&A

157

172

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Context. We present detection and analysis of faint X-ray sources in the Chandra deep field south (CDFS) using the 4 Ms Chandra observation. Aims. We place constraints on active galactic nuclei (AGN) luminosity functions at z = 3-7, its cosmological evolution, and highredshift black hole and AGN demography. Methods. We use a new detection algorithm, using the entire three-dimensional data-cube (position and energy), and searching for X-ray counts at the position of high-z galaxies in the GOODS-South survey.Results. This optimized technique results in the identification of 54 AGN at z > 3, 29 of which are new detections. Applying stringent completeness criteria, we derive AGN luminosity functions in the redshift bins 3-4, 4-5, and >5.8 and for 42.75 < log L(2-10 keV) < 44.5. We combine this data with the luminous AGN luminosity functions from optical surveys and find that the evolution of the high-z, wide luminosity range luminosity function can be modeled by pure luminosity evolution with L * decreasing from 6.6 × 10 44 erg/s at z = 3 to L * = 2 × 10 44 erg/s at z = 6. We compare the high-z luminosity function with the predictions of theoretical models using galaxy interactions as AGN triggering mechanism. We find that these models are broadly able to reproduce the high-z AGN luminosity functions. Closer agreement is found when we assume a minimum dark matter halo mass for black hole formation and growth. We compare our AGN luminosity functions with galaxy mass functions to derive the high-z AGN duty cycle, using observed Eddington ratio distributions to derive black hole masses. We find that the duty cycle increases with galaxy stellar mass and redshift by a factor of 10-30 from z = 0.25 to z = 4-5. We also report the detection of a large fraction of highly obscured, Compton thick AGN at z > 3 (18 +17 −10 %). Their optical counterparts do not show any reddening and we thus conclude that the size of the X-ray absorber is likely smaller than the dust sublimation radius. We finally report the discovery of a highly star-forming galaxy at z = 3.47, arguing that its X-ray luminosity is likely dominated by stellar sources. If confirmed, this would be one of the farthest objects in which stellar sources have been detected in X-rays.

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Section: Discussionsupporting

confidence: 77%

Faint high-redshift AGN in theChandradeep field south: the evolution of the AGN luminosity function and black hole demography

Fiore

Puccetti²,

Grazian

et al. 2011

A&A

157

172

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“…As recently discussed by Fontanot et al (2007), the surface density inferred from the luminosity function of Fan et al (2004) and Shankar & Mathur (2007) predicts that only a few luminous sources will be detected in the field of view of even the largest and deepest future surveys such as James Webb Space Telescope (JWST), and EUCLID. Our predictions suggest that these detections will be even rarer than simple empirical extrapolations predict.…”

Section: Predictions For Z >mentioning

confidence: 92%

“…In this paper, we take a further step by jointly considering the evolution of the BH-halo relation and the BH mass function, as constrained by the observed AGN luminosity function and clustering. We examine constraints on the host halos, duty cycles, radiative efficiencies, and mean Eddington ratios of massive BHs at z > 3, imposed by the clustering measurements of S07 and by a variety of measurements of the quasar luminosity function at 3 z 6 (e.g., Kennefick et al 1995;Pei 1995;Fan et al 2001Fan et al , 2004Barger et al 2003;Wolf et al 2003;Hunt et al 2004;Barger & Cowie 2005;La Franca et al 2005;Nandra et al 2005;Cool et al 2006;Richards et al 2006a;Bongiorno et al 2007;Fontanot et al 2007;Shankar & Mathur 2007;Silverman et al 2008;Shankar et al 2010;F. Shankar et al 2010, in preparation).…”

Section: Introductionmentioning

confidence: 99%

On the Radiative Efficiencies, Eddington Ratios, and Duty Cycles of Luminous High-Redshift Quasars

Shankar¹,

Crocce²,

Miralda-Escudé³

et al. 2010

ApJ

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134

184

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We investigate the characteristic radiative efficiency , Eddington ratio λ, and duty cycle P 0 of high-redshift active galactic nuclei (AGNs), drawing on measurements of the AGN luminosity function at z = 3-6 and, especially, on recent measurements of quasar clustering at z = 3-4.5 from the Sloan Digital Sky Survey. The free parameters of our models are , λ, and the normalization, scatter, and redshift evolution of the relation between black hole (BH) mass M BH and halo virial velocity V vir . We compute the luminosity function from the implied growth of the BH mass function and the quasar correlation length from the bias of the host halos. We test our adopted formulae for the halo mass function and halo bias against measurements from the large N-body simulation developed by the MICE collaboration. The strong clustering of AGNs observed at z = 3 and, especially, at z = 4 implies that massive BHs reside in rare, massive dark matter halos. Reproducing the observed luminosity function then requires high efficiency and/or low Eddington ratio λ, with a lower limit (based on 2σ agreement with the measured z = 4 correlation length)0.7λ/(1 + 0.7λ), implying 0.17 for λ > 0.25. Successful models predict high duty cycles, P 0 ∼ 0.2, 0.5, and 0.9 at z = 3.1, 4.5, and 6, respectively, and they require that the fraction of halo baryons locked in the central BH is much larger than the locally observed value. The rapid drop in the abundance of the massive and rare host halos at z > 7 implies a proportionally rapid decline in the number density of luminous quasars, much stronger than simple extrapolations of the z = 3-6 luminosity function would predict. For example, our most successful model predicts that the highest redshift quasar in the sky with true bolometric luminosity L > 10 47.5 erg s −1 should be at z ∼ 7.5, and that all quasars with higher apparent luminosities would have to be magnified by lensing.

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“…While not numerous enough at z 6 to have contributed significantly to H i reionisation (e.g. Meiksin 2005;Jiang et al 2008;Shankar & Mathur 2007;Willott et al 2010;Fontanot et al 2012Fontanot et al , 2014, they are likely the only sources responsible for the reionisation of He ii at z ∼ 3 (Miralda-Escudé et al 2000;Faucher-Giguère et al 2008;Furlanetto 2009;McQuinn et al 2009;Haardt & Madau 2012;Compostella et al 2013). All these studies rely on parameterizations of the quasar SED in the BBB region motivated by existing observations, the uncertainties of which are rarely discussed.…”

Section: Introductionmentioning

confidence: 99%

The first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from WFC3

Lusso

Worseck

Hennawi

et al. 2015

Monthly Notices of the Royal Astronomical Society

273

355

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The ionising continuum from active galactic nuclei (AGN) is fundamental for interpreting their broad emission lines and understanding their impact on the surrounding gas. Furthermore, it provides hints on how matter accretes onto supermassive black holes. Using HST's Wide Field Camera 3 we have constructed the first stacked ultraviolet (rest-frame wavelengths 600-2500Å) spectrum of 53 luminous quasars at z 2.4, with a state-of-the-art correction for the intervening Lyman forest and Lyman continuum absorption. The continuum slope (f ν ∝ ν αν ) of the full sample shows a break at ∼912Å with spectral index α ν = −0.61 ± 0.01 at λ > 912Å and a softening at shorter wavelengths (α ν = −1.70 ± 0.61 at λ 912Å). Our analysis proves that a proper intergalactic medium absorption correction is required to establish the intrinsic continuum emission of quasars. We interpret our average ultraviolet spectrum in the context of photoionisation, accretion disk models, and quasar contribution to the ultraviolet background. We find that observed broad line ratios are consistent with those predicted assuming an ionising slope of α ion =−2.0, similar to the observed ionising spectrum in the same wavelength range. The continuum break and softening are consistent with accretion disk plus X-ray corona models when black hole spin is taken into account. Our spectral energy distribution yields a 30% increase to previous estimates of the specific quasar emissivity, such that quasars may contribute significantly to the total specific Lyman limit emissivity estimated from the Lyα forest at z < 3.2.

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On the Faint End of the High‐Redshift Active Galactic Nucleus Luminosity Function

Cited by 51 publications

References 68 publications

Faint high-redshift AGN in theChandradeep field south: the evolution of the AGN luminosity function and black hole demography

Faint high-redshift AGN in theChandradeep field south: the evolution of the AGN luminosity function and black hole demography

On the Radiative Efficiencies, Eddington Ratios, and Duty Cycles of Luminous High-Redshift Quasars

The first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from WFC3

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