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Qingjuan Yu UC Berkeley April 21, 2006

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). (Tremaine et al. 2002). NGC 4258. Galactic center.

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Qingjuan Yu UC Berkeley April 21, 2006

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  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. (Tremaine et al. 2002) NGC 4258 Galactic center Quasar PKS 2349 (HST) M87 (HST) 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.) M87 (HST) Quasar PKS 2349 (HST)

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

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

  5. Extracting evolution of accretion from observations Statistical methods involving a large sample of QSOs/AGNs are required. • 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

  6. Local BHs with present-day mass M0: Triggering history: seed BHs triggered at cosmic time ti; Luminosity evolution (M0,)as a function of =t-ti; • (M0,) is isolated by connecting QSOLF with local BHs: (ignoring BH mergers)  QSOLF local BHMF lifetime probability (Yu & Lu 2004)  O t Extracting () QSOLF

  7. (M0,) L+dL L life  Luminosity evolution of individual triggered nuclei seed BH triggered QSOLF local BHMF lifetime probability

  8. (M0,) L+dL L seed BH triggered  QSOLF local BHMF lifetime probability

  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. I II I  Accretion rate distribution of SDSS nearby AGNs • Assumed accretion rate evolution:

  12. I II I  Accretion rate distribution of SDSS nearby AGNs • Assumed accretion rate evolution: (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 (Lbol/Ledd) in QSOs/AGNs (Mclure & Dunlop 2004) The diversity in the Eddington ratios is a natural result of the long-term evolution of accretion disks in AGNs. (Woo & Urry 2002)

  17. 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 Discussions

  18. 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

  19. 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.

  20. 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?

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