1 / 20

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.

terra
Télécharger la présentation

Qingjuan Yu UC Berkeley April 21, 2006

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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?

More Related