The Fall of the Quasar Population

Cavaliere, A.; Vittorini, V.

doi:10.1086/317155

Cited by 115 publications

(139 citation statements)

References 73 publications

(71 reference statements)

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“…(4)); in this case, the HQ11 model describes the corresponding mass inflow attainable in the galaxy nucleus. On the other hand, the IT model corresponds to a scenario where the large quantities of gas destabilized during encounters cannot be regarded as disk perturbations, and derives the corresponding nuclear feeding from the model by Cavaliere & Vittorini (2000).…”

Section: Discussionmentioning

confidence: 99%

“…The fraction f of cold gas destabilized by any kind of merging or interaction has been worked out by Cavaliere & Vittorini (2000) in terms of the variation ∆ j of the specific angular momentum j ≈ GM/V d of the gas to read (Menci et al 2004) as…”

Section: The Interaction-driven Modelmentioning

confidence: 99%

“…In turn, this requires an analytical description of such processes to be implemented into existing semi-analytic models (see Baugh 2006 for an introduction) or as sub-grid physics in cosmological simulations. As for the IT scenario, multi-scale high-resolution hydrodynamical N-body simulations are now resolving scales ∼10 pc, showing that collisions efficiently cause most of the gas to flow to the centre on timescales of a few dynamical times (see Hopkins et al 2010 and references therein); analytical -though simplified -or phenomenological descriptions of the inflow determined by mergers have been developed by several authors (see, e.g., Makino & Hut 1997;Cavaliere & Vittorini 2000) and then calibrated and tested against binary hydrodynamic merger simulations (Robertson et al 2006a,b;Cox et al 2006;Hopkins et al 2007b); here the fraction of galactic gas which is able to lose angular momentum and flow to the centre is related to large relative variations ∆ j/ j of the gas specific angular momentum induced by the interactions, which is in turn connected to the mass ratio M /M of the merging partners.…”

Section: Introductionmentioning

confidence: 99%

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Triggering active galactic nuclei in hierarchical galaxy formation: disk instability vs. interactions

Menci

Gatti

Fiore

et al. 2014

A&A

141

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Using a state-of-the-art semi analytic model for galaxy formation, we investigated in detail the effects of black hole (BH) accretion triggered by disk instabilities (DI) in isolated galaxies on the evolution of the AGN population. Specifically, we took on, developed, and expanded the Hopkins & Quataert (2011, MNRAS, 411, 1027 model for the mass inflow following disk perturbations, based on a physical description of nuclear inflows and tested against aimed N-body simulations. We compared the evolution of AGN due to such a DI accretion mode with that arising in a scenario where galaxy interactions (IT mode) produce the sudden destabilization of large quantities of gas feeding the AGN; this constitutes the standard AGN feeding mode implemented in the earliest versions of most semi-analytic models. To study the maximal contribution of DI to the evolution of the AGN population, we extended and developed the DI model to assess the effects of changing the assumed disk surface density profile, and to obtain lower limits for the nuclear star formation rates associated to the DI accretion mode. We obtained the following results: i) For AGN with luminosity M 1450 > ∼ −26, the DI mode can provide the BH accretion needed to match the observed AGN luminosity functions up to z ≈ 4.5. In such a luminosity range and redshift, it constitutes a viable candidate mechanism to fuel AGN, and can compete with the IT scenario as the main driver of cosmological evolution of the AGN population. ii) The DI scenario cannot provide the observed abundance of high-luminosity QSO with M 1450 ≤ −26 AGN, as well as the abundance of high-redhshift z > ∼ 4.5 QSO with M 1450 ≤ −24. As found in our earliest works, the IT scenario provides an acceptable match to the observed luminosity functions up to z ≈ 6. iii) The dispersion of the distributions of Eddington ratio λ for low-and intermediate-luminosity AGN (bolometric L AGN = 10 43 −10 45 erg s −1 ) is predicted to be much smaller in the DI scenario compared to the IT mode. iv) The above conclusions concerning the DI mode are robust with respect to the explored variants of the DI model. We discuss the physical origin of our findings. Finally, we discuss how it is possible to pin down the dominant fueling mechanism of AGN in the low-intermediate luminosity range M 1450 > ∼ −26 where the DI and the IT modes are both viable candidates as the main drivers of the AGN evolution. We show that an interesting discriminant could be provided by the fraction of AGN with high Eddington ratios λ ≥ 0.5, since it increases with luminosity in the IT case, while the opposite is true in the DI scenario.

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Section: Discussionmentioning

confidence: 99%

Section: The Interaction-driven Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Triggering active galactic nuclei in hierarchical galaxy formation: disk instability vs. interactions

Menci

Gatti

Fiore

et al. 2014

A&A

141

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“…In this paper, we discuss in more detail the fourth and final issue. Two main scenarios for AGN triggering and feeding have been investigated to date: galaxy encounters (Barnes & Hernquist 1996;Cavaliere & Vittorini 2000;Menci et al 2006Menci et al , 2008 and recycled gas produced by normal stellar evolution in the inner bulge (Ciotti & Ostriker 2007;Ciotti et al 2010;Cen 2011). These have different predictions about the AGN time scale and duty cycle.…”

Section: Introductionmentioning

confidence: 99%

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

156

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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“…We have recently introduced a more detailed treatment of the transfer of stellar mass to the bulge during major mergers, following Hopkins et al (2009): in particular, we assume that in mergers with M * 1 /M * 2 > ∼ 0.2 only a fraction 1 − f gas of the disk mass is transferred to the bulge. The fraction f of cold gas destabilized by any kind of merging or interaction has been calculated by Cavaliere & Vittorini (2000) in terms of the variation ∆ j of the specific angular momentum j ≈ GM/V d of the gas as (Menci et al 2004) f ≈ 1 2…”

Section: Agn Triggeringmentioning

confidence: 99%

Physical properties of AGN host galaxies as a probe of supermassive black hole feeding mechanisms

Gatti¹,

Lamastra²,

Menci³

et al. 2015

A&A

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Using an advanced semi-analytical model (SAM) for galaxy formation, we investigated the statistical effects of assuming two different mechanisms for triggering AGN activity on the properties of AGN host galaxies. We considered a first accretion mode where AGN activity is triggered by disk instabilities (DI) in isolated galaxies, and a second feeding mode where galaxy mergers and fly-by events (interactions, IT) are responsible for producing a sudden destabilization of large quantities of gas, causing the mass inflow onto the central supermassive black hole. The effects of including IT and DI modes in our SAM were studied and compared with observations separately to single out the regimes in which they might be responsible for triggering AGN activity. We obtained the following results: i) the predictions of our model concerning the stellar mass functions of AGN hosts point out that both DI and IT modes are able to account for the observed abundance of AGN host galaxies with M * < ∼ 10 11 M ; for more massive hosts, the DI scenario predicts a much lower space density than the IT model in every redshift bin, lying below the observational estimates for redshift z > 0.8. ii) The analysis of the colour−magnitude diagram of AGN hosts for redshift z < 1.5 can provide a good observational test to effectively distinguish between DI and IT mode, since DIs are expected to yield AGN host galaxy colours skewed towards bluer colours, while in the IT scenario the majority of hosts are expected to reside in the red sequence. iii) While both IT and DI scenarios can account for AGN triggered in main sequence or starburst galaxies, DIs fail in triggering AGN activity in passive galaxies. The lack of DI AGN in passive hosts is rather insensitive to changes in the model describing the DI mass inflow, and it is mainly caused by the criterion for the onset of disk instabilities included in our SAM. iv) The two modes are characterized by a different duration of the AGN phase, with DIs lasting even on time scales of ∼Gyr, much longer than in the IT scenario, where the galaxy interaction sets the duration of the burst phase around ∼10 7 −10 8 yr. v) The scatter of the star formation rate SFR−L bol relation could represent another crucial diagnostics to distinguish between the two AGN triggering modes, since the DI scenario predicts an appreciably lower scatter (especially at lowto-intermediate AGN luminosities) of the relation than the IT scenario. vi) Disk instabilities are unable to account for the observed fraction of AGN in groups for z < ∼ 1 and clusters for z < ∼ 0.7, while the IT scenario matches observational data well.

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The Fall of the Quasar Population

Cited by 115 publications

References 73 publications

Triggering active galactic nuclei in hierarchical galaxy formation: disk instability vs. interactions

Triggering active galactic nuclei in hierarchical galaxy formation: disk instability vs. interactions

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

Physical properties of AGN host galaxies as a probe of supermassive black hole feeding mechanisms

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