Accretion-driven evolution of black holes: Eddington ratios, duty cycles and active galaxy fractions

By Francesco Shankar, D. Weinberg, J. París, Cnrs, U. Diderot, O. University, I. C. D. R. I. E. Avançats, Institut de Ci'encies del Cosmos, U. Barcelona. 2011

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We develop semi-empirical models of the supermassive black hole and active galactic nucleus (AGN) populations, which incorporate the black hole growth implied by the observed AGN luminosity function assuming a radiative efficiencyǫ and a distribution of Eddington ratios λ. By generalizing these continuity-equation models to allow a distribution P(λ|MBH,z) we are able to draw on constraints from observationally estimated λ distributions and active galaxy fractions while accounting for the luminosity thresholds of observational samples. We consider models with a Gaussian distribution of logλ and Gaussians augmented with a power-law tail to low λ. Within our framework, reproducing the high observed AGN fractions at low redshift requires a characteristic Eddington ratio λc that declines at late times, and matching observed Eddington ratio distributions requires a P(λ) that broadens at low redshift. To reproduce the observed increase of AGN fraction with black hole or galaxy mass, we also require a λc that decreases with increasing black hole mass, reducing the AGN luminosity associated with the most massive black holes. Finally, achieving a good match to the high mass end of the local black hole mass function requires an increased radiative efficiency at high black hole mass. We discuss the potential impact of black hole mergers or a λ-dependent bolometric correction, and we compute evolutionary predictions for black hole and galaxy specific accretion rates. Despite the flexibility of our framework, no one model provides a good fit to all the data we consider; it is particularly difficult to reconcile the relatively narrowλ distributions and low duty cycles estimated for luminous broad-line AGN with the broader λ distributions and higher duty cycles found in more widely selected AGN samples, which typically have lower luminosity thresholds.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6a8403f15fc9e7d44252a960feb8bf111e3d474b

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Citations in the corpus

TOWARD THE STANDARD POPULATION SYNTHESIS MODEL OF THE X-RAY BACKGROUND: EVOLUTION OF X-RAY LUMINOSITY AND ABSORPTION FUNCTIONS OF ACTIVE GALACTIC NUCLEI INCLUDING COMPTON-THICK POPULATIONS (2014, background): “…1992; Yu & Tremeine 2012; Marconi et al. 2004; Shankar et al. 2004; Tamura et al. 2006; Cao & Li 2008; Shankar et al. 2009; Li et al. 2012; Shankar et al. 2013), it is also possible to trace the cosmological evolution of the mass function (MF) of all SMBHs including both active (i.e.,…”
The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe (2014, methodology): “…in the introduction, the ratio of the rate of build-up of galaxies through star formation to the rate of the build-up of black holes via accretion has been broadly independent of cosmic time over at least the last ∼ 10Gyrs with a value of ∼1500 (Shankar et al. 2009, 2013, Hopkins & Beacom 2006).”
AGN wind scaling relations and the co-evolution of black holes and galaxies (2017, methodology): “This was done using the results briefly presented in the previous section and in Shankar et al. (2013, 2016).”
BLACK HOLE VARIABILITY AND THE STAR FORMATION–ACTIVE GALACTIC NUCLEUS CONNECTION: DO ALL STAR-FORMING GALAXIES HOST AN ACTIVE GALACTIC NUCLEUS? (2013, methodology): “…be effective at modeling the quasar luminosity function (LF), clustering, and other observables (e.g. Shankar et al. 2013; Conroy & White 2013), although they do not reproduce observed Eddington ratio distributions for moderateluminosity AGNs (e.g., Hopkins & Hernquist 2009; Shankar et al. 2013).”
Selection bias in dynamically measured supermassive black hole samples: its consequences and the quest for the most fundamental relation (2016, methodology): “…2014; Sesana et al. 2014; Aversa et al. 2015; Fontanot et al. 2015; Sijacki et al. 2015), as well as on the average radiative efficiencies/black hole spin and/or fraction of obscured sources (e.g., Soltan 1982; Elvis et al. 2002; Shankar et al. 2013b; Aversa et al. 2015; Tucci & Volonteri 2016).”