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Why Massive Black Holes are Small in Disk Galaxies ?

Why Massive Black Holes are Small in Disk Galaxies ?. Nozomu KAWAKATU Center for Computational Physics, University of Tsukuba. Collaborator. Masayuki UMEMURA. Center for Computational Physics, University of Tsukuba.

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Why Massive Black Holes are Small in Disk Galaxies ?

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  1. Why Massive Black Holes are Small in Disk Galaxies ? Nozomu KAWAKATU Center for Computational Physics, University of Tsukuba Collaborator Masayuki UMEMURA Center for Computational Physics, University of Tsukuba Formation of the First Generation of Galaxies: Strategy for the Observational Corroboration of Physical Scenarios, 2-5 December 2003, Niigata University, Niigata, Japan

  2. Contents • Introduction Recent observational results ( BH mass-to-bulge mass correlation ) Angular momentum transfer problem for supermassive black holes • Physical mechanism for formation of Supermassive Black Holes Radiation drag (Poynting-Robertson) effect • Basic Equation Equation of angular momentum transfer Treatment for extinction by dusty gas • Model for Disk galaxies • Results Relationship between the final BH mass and bulge-to-disk ratio of host galaxy • Summary

  3. 1) BH mass-to-galaxy mass ratio is considerably smaller than 0.002 for Disk. (Salucci et al. 2000; Sarzi et al. 2001; Ferrarese 2002; Baes et al. 2003) Introduction Recent high quality observations of galactic centers 2) BH mass-to-galaxy mass ratio is reduced by more than an order of magnitude with a smaller bulge-to-disk ratio. 10-2 × Normal spiral and barred galaxies Sy2 ▲ Sy1 NLSy1 10-3 MBH / Mgalaxy 10-4 10-5 0.03 1 0.1

  4. ellipticals = Formation of SMBHs Formation of Bulges Physical relation! 3) BH mass-to-bulge mass ratio lies at a level of 0.001, which is similar to that found in elliptical galaxies. (e.g., Kormendy & Richstone 1995) 10-2 10-3 MBH / Mbulge 10-4 × Normal spiral and barred galaxies 10-5 Sy2 ▲ Sy1 NLSy1 0.03 1 0.1

  5. It has not been clear why the BH mass is smaller in disk physically!! Summary of observational results in galactic centers Elliptical Galaxies Disk Galaxies

  6. Hydrodynamical Mechanisms for Ang. Mom. Transfer ( From galactic scale to BH horizontal scale ) 1) Gravitational torque by a bar or non-axisymmetric mode But, this mechanism is effective only beyond ~ 1kpc. (Wada & Habe 1995, Fukuda 1998) 2) Turbulent viscosity But, the timescale is longer than the Hubble time in galactic scale ! (e.g. A galactic disk cannot shrink via turbulent viscosity.) 3) Radiation drag (present work) theoretical upper limit: (Umemura 2001) The timescale is shorter than the Hubble time in galactic scale. SMBH Formation: Angular Momentum Problem The physics on the angular momentum transfer is essential !

  7. Lab.Frame < Re-emission process > “radiation drag” v0 v Matter slowdowns ! v < v0 Radiation Drag –Poynting-Robertson Effect– Lab.Frame < Absorption process > In practice, optically thin surface layer is stripped by radiation drag, and loses angular momentum (Sato-san talks in details).

  8. Radiation Drag efficiency in galactic bulges Optically thick regime “Radiation drag efficiency is determined by the total number of photons ” :total luminosity of the bulge 1) The BH-to-bulge mass ratio is basically determined by the energy conversion efficiency of nuclear fusion from hydrogen to helium, i.e., 0.007. (Umemura 2001) 2) The inhomogeneity of ISM helps the radiation drag to sustain the maximal efficiency. (Kawakatu & Umemura 2002 ) covering factor O(1) ISM is observed to highly inhomogeneous in active star-forming galaxies ! 3) By incorporating the realistic chemical evolution, we predicted . (Kawakatu, Umemura & Mori 2003 )

  9. Radiation drag - Geometrical Dilution - (Umemura et al. 1997,1998; Ohsuga et al. 1999) Spherical System Disk-like System low drag efficiency high drag efficiency However, the details are not clear quantitatively !

  10. This Work We investigate the efficiency of radiation drag in disk galaxies. We solve the 3D radiation transfer in an inhomogeneous ISM. To investigate the relation between the morphology of host galaxies and the angular momentum transfer efficiency due to the radiation drag We have disclosed the physical reasons why the BHs are smaller in disk galaxies!

  11. Model 1 The difference of morphology is expressed by changing“ bulge fraction (fbulge)”. fbulge 0.5 Inhomogeneous ISM covering factor is unity. 0.03 “disk scale height “

  12. Radiation Drag Radiation Flux Basic Equations The Eq.of Ang.Mom.Transfer ： mass extinction due to dust opacity radiation stress tensor radiation energy density radiation flux The gain and loss of total angular momentum is regulated by this equation. The contribution of the radiation from distant stars is essential to radiation drag since these stars have different velocities from absorbing clouds.

  13. We calculate the radiation fields by the direct integration of the radiation transfer. Treatment of the radiation tranfser All radiative quantities are determined by radiation from stars diluted by dusty ISM. opacity :dust in clumpy gas clouds ：the optical depth for all intervening clouds along the light ray :optical depth of a gas cloud

  14. Angular momentum transfer in an Inhomogeneous ISM Total angular momentum loss rate ( Nc:Number of clouds) Mass Accretion Rate Angular Momentum Extraction Total mass of the ISM Estimate for BH mass ( t0:Hubble time; J: total angular momentum )

  15. Hubble Type Sc Sd Sb Sa E S0 Almost constant 10-3 Mass ratio 10-4 ～1/20 ～1/50 10-5 ～1/200 0.03 0.1 1 Result.1: BH mass-to-morphology relation

  16. Why MBH are small in disk galaxies？ ① & ② ③ “radiation” pole on view ① A number of photons escaped from the system(Surface-to-volume ratio ) ② Radiation from disk stars is heavily diminished across the disk(optically thick disk) ③ The velocity difference stars and absorbing clouds becomes closer to zero(optically thick disk) Radiation drag cannot work effectively in disk galaxies !

  17. 10-2 × Normal spiral and barred galaxies NGC3227 ▲ Sy1 Sy2 NLSy1 × × Normal spiral and barred galaxies Normal spiral and barred galaxies NGC3245 NGC3227 NGC3227 ▲ ▲ Sy1 Sy1 Sy2 Sy2 NLSy1 NLSy1 NGC4151 M31 NGC3245 NGC3245 NGC5548 NGC3783 10-3 M81 NGC4151 NGC4151 M31 M31 NGC1023 NGC5548 NGC5548 NGC3783 NGC3783 M81 M81 NGC4258 Mrk509 NGC4593 MBH / Mgalaxy NGC1023 NGC1023 Fairall 9 NGC3516 NGC4258 NGC4258 Mrk509 Mrk509 NGC4593 NGC4593 NGC4395 3C120 Galaxy Fairall 9 Fairall 9 (Sy2/Starburst) 10-4 NGC3516 NGC7457 NGC4395 NGC4395 3C120 3C120 NGC7469 Galaxy Galaxy (Sy2/Starburst) (Sy2/Starburst) (Sy1/Starburst) NGC7457 NGC7457 Mrk590 NGC7469 NGC7469 Mrk590 Mrk590 NGC1068 (Sy1/Starburst) (Sy1/Starburst) (Sy2/Starburst) NGC4051 NGC4051 NGC4051 10-5 Circinus (Sy2/Starburst) NGC1068 NGC1068 (Sy2/Starburst) (Sy2/Starburst) 1 0.03 0.1 Circinus Circinus (Sy2/Starburst) (Sy2/Starburst) Result.2-1: Comparison with the observations These objects have relatively small BHs compared with the predictions. This trend is broadly consistent with theoretical prediction.

  18. 10-2 NGC3227 NGC4258 NGC4151 M31 M81 NGC3245 NGC3227 NGC3227 NGC4258 NGC4258 NGC3783 NGC4395 NGC5548 NGC4151 NGC4151 M31 M31 NGC1023 M81 M81 NGC3245 NGC3245 (Sy2/Starburst) Fairall 9 NGC5548 NGC5548 NGC3783 NGC3783 NGC4395 NGC4395 Mrk509 NGC1023 NGC1023 10-3 (Sy2/Starburst) (Sy2/Starburst) Fairall 9 Fairall 9 NGC1068 Galaxy NGC4593 (Sy2/Starburst) 3C120 Mrk509 Mrk509 NGC1068 NGC1068 Galaxy Galaxy NGC4593 NGC4593 MBH / Mbulge NGC3516 (Sy2/Starburst) (Sy2/Starburst) 3C120 3C120 Circinus NGC7457 (Sy2/Starburst) NGC4051 NGC3516 NGC3516 NGC7469 10-4 Circinus (Sy2/Starburst) Circinus NGC7457 NGC7457 (Sy2/Starburst) (Sy1/Starburst) Mrk590 NGC4051 NGC4051 NGC7469 NGC7469 (Sy1/Starburst) (Sy1/Starburst) Mrk590 Mrk590 × Normal spiral and barred galaxies 10-5 ▲ Sy2 NLSy1 Sy1 × × Normal spiral and barred galaxies Normal spiral and barred galaxies 0.03 0.1 1 ▲ ▲ Sy2 Sy2 Sy1 Sy1 NLSy1 NLSy1 Result.2-2: Comparison with the observations Observational data roughly agree with the prediction . Sy1 with SB & NLSy1 fall appreciably below 0.001 again.

  19. Summary １．BH-to-galaxy mass ratio decreases with a smaller bulge-to-disk ratio, and is reduced maximally by two orders of magnitude, resulting in . The present model also predict BH-to-galaxy mass ratio depends on the disk scale-height (h), ＜Physical Reasons＞ • Almost all photons can escape from a disk-like system, owing to the effect of geometrical dilution. • The radiation from stars in disk galaxies is considerably reduced in the optically-thick disk. • The velocity difference stars and absorbing clouds becomes closer to zero ２．In disk galaxies, the BH-to-bulge mass ratio is about 0.001 . It turns out that the formation of SMBH is not basically determined by disk components, but bulge components, consistently observational data. The BH-to-bulge mass ratio is fundamentally determined by physical constantε=0.007, regardless of morphology of host galaxies.

  20. Grazie mille! どうもありがとう ございました！

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