Evolution of luminosity function and obscuration of AGN: connecting X-ray and Infrared

Abstract

We present a detailed comparison between the 2-10 keV hard X-ray and infrared (IR) luminosity function (LF) of active galactic nuclei (AGN). The composite X-ray to IR spectral energy distributions (SEDs) of AGN used for connecting the hard X-ray LF (HXLF) and IR LF (IRLF) are modeled with a simple but well tested torus model based on the radiative transfer and photoionization code CLOUDY. Four observational determinations of the evolution of 2-10 keV HXLF and six evolution models of the obscured type-2 AGN fraction ($f_2$) have been considered. The 8.0 and 15 \micron LFs for the total, unobscured type-1 and obscured type-2 AGN are predicted from the HXLFs, and then compared with the measurements currently available. We find that the IRLFs predicted from HXLFs tend to underestimate the number of the most IR-luminous AGN. This is independent of the choices of HXLF and $f_2$, and even more obvious for the HXLFs recently measured. We show that the discrepancy between the HXLFs and IRLFs can be largely resolved when the anticorrelation between the UV to X-ray slope ${\alpha }_{\mathrm{ox}}$ and UV luminosity $L_{\mathrm{UV}}$ is appropriately considered. We also discuss other possible explanations for the discrepancy, such as the missing population of Compton-thick AGN and possible contribution of star-formation in the host to the mid-IR. Meanwhile, we find that the HXLFs and IRLFs of AGN can be more consistent with each other if the obscuration mechanisms of quasars and Seyferts are assumed to be different, corresponding to their different triggering and fueling mechanisms. More accurate measurements of the IRLFs of AGN, especially that determined at smaller redshift bins and more accurately separated to that for type-1 and type-2, are very helpful for clarifying these interesting issues.

15 pages, 11 figures, accepted for publication in MNRAS

References in corpus (28)

• The Host Galaxies and Classification of Active Galactic Nuclei
• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: I. Galaxy Mergers & Quasar Activity
• An Observational Determination of the Bolometric Quasar Luminosity Function
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• AGN Dusty Tori: I. Handling of Clumpy Media
• Direct cosmological simulations of the growth of black holes and galaxies
• The X-ray-to-Optical Properties of Optically-Selected Active Galaxies Over Wide Luminosity and Redshift Ranges
• X-ray spectral properties of AGN in the Chandra Deep Field South
• Absorption Properties and Evolution of Active Galactic Nuclei
• Spitzer Quasar and ULIRG Evolution Study (QUEST): II. The Spectral Energy Distributions of Palomar-Green Quasars
• The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift
• How Mergers May Affect The Mass Scaling Relations Between Black Holes, Galaxies, and Other Gravitationally Bound Systems
• Radiative Transfer Modeling of Three-Dimensional Clumpy AGN Tori and its Application to NGC 1068
• The Star-Forming Torus and Stellar Dynamical Black Hole Mass in the Seyfert 1 Nucleus of NGC3227
• An Observed Fundamental Plane Relation for Supermassive Black Holes
• The Evolution of Obscuration in AGN
• Luminosity functions for galaxies and quasars in the Spitzer Wide-Area Infrared Extra-galactic (SWIRE) Legacy survey
• The VVDS type-1 AGN sample: The faint end of the luminosity function
• Breaking the law: the M_{bh}-M_{spheroid} mass relations for core-Sersic and Sersic galaxies
• The mid IR -- hard X-ray correlation in AGN and its implications for dusty torus models
• The Correlation of Narrow Line Emission and X-ray Luminosity in Active Galactic Nuclei
• The XMM-Newton Serendipitous Survey. VI. The X-ray Luminosity Function
• The Luminosity Function of high-redshift QSOs - A combined analysis of GOODS and SDSS
• Obscuring Active Galactic Nuclei with Nuclear Starburst Disks
• The Unified Model of Active Galactic Nuclei: I. Non-hidden Broad Line Region Seyfert 2 and Narrow Line Seyfert 1 Galaxies
• The small dispersion of the mid IR -- hard X-ray correlation in AGN
• Variability and the X-ray/UV ratio of Active Galactic Nuclei
• Does the AGN Unified Model Evolve with Redshift? Utilizing the X-ray Background to Predict the Mid-Infrared Emission of AGN

Cited by in corpus (9)

• The Spitzer mid-infrared AGN survey. II-the demographics and cosmic evolution of the AGN population
• Obscuring Fraction of Active Galactic Nuclei: Implications from Radiation-driven Fountain Models
• BayeSED: A General Approach to Fitting the Spectral Energy Distribution of Galaxies
• The XXL Survey: VI. The 1000 brightest X-ray point sources
• The Past and Future of Mid-Infrared Studies of AGN
• A Joint Model of the X-ray And Infrared Extragalactic Backgrounds: I. Model Construction And First Results
• Evidence that Emission and Absorption Outflows in Quasars Are Related
• Mid-infrared Spectral Properties of Post-Starburst Quasars
• Hot graphite dust in the inner regime of NGC 4151