modeling agn properties in the local universe

Federico Marulli, Dipartimento di Astronomia, Università di Bologna

Modeling AGN properties in Modeling AGN properties in the local Universethe local Universe

Federico MarulliDipartimento di Astronomia

Università degli Studi di Bologna

Modeling active galactic nuclei: ongoing problems for the faint-end of Modeling active galactic nuclei: ongoing problems for the faint-end of the luminosity functionthe luminosity function

F.Marulli, E.Branchini, L.Moscardini, M.Volonteri (MNRAS,375,649) F.Marulli, E.Branchini, L.Moscardini, M.Volonteri (MNRAS,375,649)


ContentsContents

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


General feauturesGeneral 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)


BH scale relationsBH scale relations


AGN bolometric luminosity AGN bolometric luminosity functionfunction


Semi-analytic modelSemi-analytic modelMethodMethod

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 Msun, z=20, Mhalo=1.6e7 Msun (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

haloaccr MM

5caccr vkM 05.0)1(15.0)( zzkk

6107


Semi-analytic modelSemi-analytic modelMethodMethod

Data and equations

220 binary merger trees of parent halos with masses in the range (1.43e11,1e15 Msun)

0 min,

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Semi-analytic modelSemi-analytic modelLuminosity functionLuminosity function


Semi-analytic modelSemi-analytic modelBiasing functionBiasing function


ConclusionsConclusions 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 ofthe hydrodynamical simulations by Hopkins et al. 2005

→ 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


LLQSOQSO-M-Mhalohalo


MMbhbh--σσ


VHM plotsVHM plots


N(M)N(M)


VHM equationsVHM equations

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modeling agn properties in the local universe

Documents

1e15 msunfederico marulli

moderate redshifts z

agn bolometric lf

supermassive black holes

given luminosity

lower redshifts

hierarchical models

agn feedback