1. Evolution of Accretion Disks around Massive Black Holes: Constraints from the Demography of Active Galactic Nuclei Qingjuan Yu UC Berkeley April 21, 2006 (2005, ApJ, 634, 901, Qingjuan Yu, Youjun Lu, & Guinevere Kauffmann)

2. Introduction QSOs are powered by gas accretion onto MBHs. Most nearby galaxies host MBHs at their centers. Mass growth of MBHs comes mainly from gas accretion due to QSO/AGN phases. (Lynden-Bell 1969; Rees 1984; Soltan 1982; Small & Blandford 1992; Kormendy & Richstone 1995; Magorrian et al. 1998; Yu & Tremaine 2002 etc.) Quasar PKS 2349 (HST) M87 (HST) Quasar PKS 2349 (HST) M87 (HST) Galactic center NGC 4258 (Tremaine et al. 2002)

3. How does the accretion/luminosity evolve? ()()  Evolution after the nuclear activity of a QSO/AGN is triggered

4. Cosmological evolution of comoving number density of the QSO population: Evolution of the characteristic luminosity of the QSO population: Not meaning

5. Extracting evolution of accretion from observations A single AGN may only represent one specific period in a prolonged phase of nuclear activity. A large sample of AGNs with different ages will span all phases of this activity and allow us to extract information about evolution. In addition to age, other physical parameters may be important in determining how AGNs evolve, and a statistical method may help to clarify these. 2dF SDSS Statistical methods involving a large sample of QSOs/AGNs are required.

6. Extracting  (  ) Local BHs with present-day mass M 0 : –Triggering history: seed BHs triggered at cosmic time t i ; –Luminosity evolution  (M 0,  ) as a function of  =t-t i ;   t O QSOLF QSOLF local BHMF lifetime probability (Yu & Lu 2004) (ignoring BH mergers)  (M 0,  ) is isolated by connecting QSOLF with local BHs:

7.  (M 0,  )   life L L+dL QSOLF local BHMF lifetime probability Luminosity evolution of individual triggered nuclei seed BH triggered

8.  (M 0,  )  L L+dL QSOLF local BHMF lifetime probability seed BH triggered

9. Accretion rate distribution of SDSS nearby AGNs (Yu, Lu & Kauffmann 2005)

10. Accretion rate distribution of SDSS nearby AGNs SDSS sample: (Kauffmann et al. 2003; Heckman et al. 2004)

11. Accretion rate distribution of SDSS nearby AGNs -Assumed accretion rate evolution:  I II II 

12. Accretion rate distribution of SDSS nearby AGNs -Assumed accretion rate evolution:  I II II  (Yu, Lu & Kauffmann 2005)

13. Evolution model of accretion disks: Evolution of surface mass density: Self-similar solutions (Pringle 1974): (Cannizzo, Lee, & Goodman 1990)

14. Evolution model of accretion disks: Diffusion timescale Consistency of observations with simple theoretical expectations suggests that the accretion process in nearby AGNs follows a self-similar evolutionary pattern.

15. T Tauri star Disk accretion: self-similar evolution (Hartmann et al. 1998)

16. Diversity of Eddington ratios (L bol /L edd ) in QSOs/AGNs (Mclure & Dunlop 2004) (Woo & Urry 2002) The diversity in the Eddington ratios is a natural result of the long-term evolution of accretion disks in AGNs.

17. Discussions Further issues related to long-term evolution of accretion disks: –Disk winds, infalling material deposited onto the disk, instabilities, self-gravitating disks, star formation … Binary black holes and coevolution of galaxies and QSOs/AGNs

18. Discussions Diffusion timescale: –Difference from QSOs; –Sensitive to R 0 : constraints on fueling mechanisms?

19. Discussions Adding the effect of an evolving accretion disk in unified models of AGNs –Lack of a torus in very weak AGNs –Radiatively inefficient accretion

20. Summary The accretion rates in most nearby Seyfert galaxies (with host galaxy velocity dispersion sigma~70-200km/s, z<0.3) are declining with time in a power-law form and the accretion process follows a self-similar evolutionary pattern as simple theoretical models predict. Some other issues deserves of further investigation, such as the long-term evolution of accretion disks, the evolution of BBHs in QSOs/AGNs, coevolution of galaxies and QSOs/AGNs, and the unification picture of AGNs.

21. Alternative explanation for the accretion rate distribution Fueling low-level AGN activity through the stochastic accretion of cold gas, astro-ph/0603180, Hopkins & Hernquist –Feed-back driven model in a large-scale context But how can the evolution of accretion disks be avoidable?