Linking X-ray AGN with dark matter halos: a model compatible with AGN luminosity function and large-scale clustering properties

Abstract

Our goal is to find a minimalistic model that describes the luminosity function and large-scale clustering bias of the X-ray-selected AGN in the general framework of the concordance LCDM model. We assume that a simple population-averaged scaling relation between the AGN X-ray luminosity L_X and the host dark matter halo mass M_h exists. With such a relation, the AGN X-ray luminosity function can be computed from the halo mass function. Using the concordance LCDM halo mass function for the latter, we obtain the M_h-L_X relation required to match the redshift-dependent AGN X-ray luminosity function known from X-ray observations. We find that with a simple power-law-scaling M_h \propto L_X^Γ(z), our model can successfully reproduce the observed X-ray luminosity function. Furthermore, we automatically obtain predictions for the large-scale AGN clustering amplitudes and their dependence on the luminosity and redshift, which seem to be compatible with AGN clustering measurements. Our model also includes the redshift-dependent AGN duty cycle which peaks at the redshift z ~ 1, and its peak value is consistent with unity, suggesting that on average there is no more than one AGN per dark matter halo. For a typical X-ray-selected AGN at z ~ 1, our best-fit M_h-L_X scaling implies low Eddington ratio L_X/L_Edd ~ 10^{-4}-10^{-3} (2-10 keV band, no bolometric correction applied) and correspondingly large mass growth e-folding times, suggesting that the typical X-ray AGN are dominantly fueled via relatively inefficient 'hot-halo' accretion mode.

extended version addressing referee comments, A&A accepted

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• The Dark Matter Halos of Moderate Luminosity X-ray AGN as Determined from Weak Gravitational Lensing and Host Stellar Masses
• Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse gamma-ray emission
• Large scale clustering measurements with photometric redshifts: comparing the dark matter halos of X-ray AGN, star-forming and passive galaxies at z~1
• The correlation of extragalactic $\gamma$-rays with cosmic matter density distributions from weak-gravitational lensing
• Cross Correlation of the Extragalactic Gamma-ray Background with Thermal Sunyaev-Zel'dovich Effect in the Cosmic Microwave Background
• Clustering, Cosmology and a New Era of Black Hole Demographics -- I. The Conditional Luminosity Function of Active Galactic Nuclei