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Federico Marulli, Dipartimento di Astronomia, Università di Bologna Modeling AGN properties in the local Universe Federico Marulli Dipartimento di Astronomia.

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Presentation on theme: "Federico Marulli, Dipartimento di Astronomia, Università di Bologna Modeling AGN properties in the local Universe Federico Marulli Dipartimento di Astronomia."— Presentation transcript:

1 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Modeling AGN properties in the local Universe Federico Marulli Dipartimento di Astronomia Università degli Studi di Bologna Modeling active galactic nuclei: ongoing problems for the faint-end of the luminosity function F.Marulli, E.Branchini, L.Moscardini, M.Volonteri (MNRAS,375,649) F.Marulli, E.Branchini, L.Moscardini, M.Volonteri (MNRAS,375,649)

2 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Contents Aim of this work  Compare the predictions of standard theoretical models to the most recent observational data at low redshifts (z<2) Observational data  Luminosity function (LF)  Clustering Theoretical models  Semi-analytic methods  Standard assumption: QSO emission triggered by galaxy mergers

3 Federico Marulli, Dipartimento di Astronomia, Università di Bologna General feautures QSOs first discoveries: Schmidt, Greenstein&Matthews in the early 60’s Accretion of mass onto supermassive black holes as the power mechanism for QSOs emission (Lynden Bell 1969) Supermassive black holes are a ubiquitous constituent of spheroids in nearby galaxies (Kormandy&Richstone 1995) The QSO population evolves with cosmic time: the QSO space density above a given luminosity increases by a factor of ~50 from the present to z~2.5, then decreases to z~5 (for istance Richards et al. 2006)

4 Federico Marulli, Dipartimento di Astronomia, Università di Bologna BH scale relations

5 Federico Marulli, Dipartimento di Astronomia, Università di Bologna AGN bolometric luminosity function

6 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Semi-analytic model Method Assumptions  Hierarchical structure formation: EPS model (Monte Carlo procedure)  QSO phenomenon is triggered by halo-halo major mergers (P:=0.1)  BHs seeds: M=150 M sun, z=20, M halo =1.6e7 M sun (3.5 σ) Kind of accretion  Coalescence of BH binary (neglected)  Gas accretion E1: E2: B: early stage of super critical accretion (Bondi-Hoyle; z>12) H: AGN feedback is included following the outcome of recent hydrodynamical simulations of galactic mergers

7 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Semi-analytic model Method Data and equations 220 binary merger trees of parent halos with masses in the range (1.43e11,1e15 Msun)

8 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Semi-analytic model Luminosity function

9 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Semi-analytic model Luminosity function

10 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Semi-analytic model Luminosity function

11 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Semi-analytic model Biasing function

12 Federico Marulli, Dipartimento di Astronomia, Università di Bologna Conclusions  We confirm the success of simple semi-analytic models in reproducing both the AGN bolometric LF at 1 < z ≤ 2, i.e. around the peak of activity, and their clustering, quantified by the biasing function, at z ≤ 2  As pointed out by several previous analyses, problems occur at lower redshifts, where hierarchical models systematically overestimate the number density of bright AGNs and underestimate the faint ones  Comparing bolometric LFs rather than the optical or hard X-rays ones allows to spot significant discrepancies already at moderate redshifts z~1, i.e. earlier than what was found in previous analyses (e.g. Marulli et al. 2006)  The underestimating of faint AGNs looks like a serious problem that we have tried to tackle by assuming a time-dependent Eddington ratio, as suggested by the outcome of the hydrodynamical simulations by Hopkins et al → hierarchical models in which accretion is driven only by major mergers cannot describe the local properties of AGNs, and accretion episodes not triggered by such mergers are likely necessary

13 Federico Marulli, Dipartimento di Astronomia, Università di Bologna

14 L QSO -M halo

15 Federico Marulli, Dipartimento di Astronomia, Università di Bologna M bh - σ

16 Federico Marulli, Dipartimento di Astronomia, Università di Bologna VHM plots

17 Federico Marulli, Dipartimento di Astronomia, Università di Bologna N(M)

18 VHM equations


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