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Astrophysical Black Holes: Key Questions and Observations

Delve into the critical queries about black holes, from their existence to evolution, accretion mechanisms, energy release forms, and their influence on galaxies and clusters. Explore the relationship between black hole mass and galactic properties, as well as intriguing observations like the Black Hole at the Galactic Center and the mass distribution of astrophysical black holes. Investigate the dynamics of gas accretion, energy output, and the impact of black holes on the broader cosmic environment.

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Astrophysical Black Holes: Key Questions and Observations

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  1. Discuss topics in sequence with the question at the top of each slide.

  2. Astrophysical Black Holes: Key Questions Avi Loeb Harvard University Fourth Sackler conference, May 15-18, 2006

  3. Key questions • Is general relativity the correct description of strong gravity?Do black holes exist?Are they described by the Kerr metric (with the predicted properties of the event horizon, innermost stable circular orbit, photon orbit, etc.)? • What is the spin and mass distribution of astrophysical black holes? Why? • What is the history of black hole formation and evolution? How did the first black holes form? Was growth dominated by accretion of gas, consumption of stars or mergers? Do binaries coalesce? What is the impact of gravitational-wave recoil? • How do black holes accrete gas? What are the geometry and radiative efficiency of the accretion flow as a function of the accretion rate? Which fraction of the infalling mass is expelled in outflows? • In what form do black holes release accretion energy? What is the relative fraction of radiation, magnetically-dominated outflows, relativistic particles, non-relativistic winds, neutrinos, gravitational waves?How are relativistic jets produced? Are they made of e+e- or baryons? • How do nuclear black holes influence the evolution of their host galaxies, X-ray clusters, or the larger-scale intergalactic medium?What is the origin of the correlations between black hole mass and spheroid properties?What sets the maximum mass of galaxies?

  4. The Black Hole in the Galactic Center: SgrA* VLT with Adaptive Optics “3-color”: 1.5 - 3 um 8.2 m VLT telescope CONICA (IR camera) NAOS (adaptive optics) 60 mas resolution

  5. Ghez et al. 2003 Genzel et al 2003 SO-16 closest approach at 90 AU Simultaneous fit of orbits implies: 1. BH mass: 2. BH proper motion: < 0.8+-0.7 mas/yr

  6. Water Masers: NGC 4258 Moran, Greenhill, & Herrnstein (2000)

  7. Keplerian Velocity Profile Miyoshi et al. 1995

  8. Is general relativity a valid description of strong gravity? *Infrared variability of flux (Genzel et al.) and polarization (Eckart et al.) of SgrA*: hot spots. *Innermost Stable Circular Orbit: radius of 30 (10) micro-arcsecond and orbital time of 30 (8) minutes for a non-rotating (maximally-rotating) black hole at the Galactic center *A hot spot would result in infrared centroid motion (PRIMA-VLT) and could be imaged by a Very Large Baseline Array of (existing) sub-millimeter observatories. Targets:SgrA* and M87 Broderick & Loeb 2005

  9. What is the spin distribution of astrophysical black holes? Contribution from Gas accretion dominates over mergers Volonteri, Madau, Quataert, & Rees (2005)

  10. What is the history of black hole formation and evolution?

  11. The First Dark Matter Objects in the Universe Smallest dark matter clumps: ~0.1 Jupiter mass Diemand, Moore & Stadel astro-ph/0501589 Loeb & Zaldarriaga, astro-ph/0504112

  12. Emergence of the First Star Clusters molecular hydrogen Yoshida et al. 2003

  13. Cooling Rate of Primordial Gas n=0.045 cm^-3 Atomic cooling H_2 cooling

  14. Virial Temperature of Halos Atomic cooling H_2 cooling 3-sigma 1-sigma 2-sigma

  15. Massive Accretion by Pop-III Proto-Stars 23.5pc 0.5pc Resolving accretion flow down to ~0.03 pc Bromm & Loeb, New Astronomy, 2004; astro-ph/0312456

  16. Formation of Massive Black Holes in the First Galaxies Add Bromm Low-spin systems: Eisenstein & Loeb 1995 Numerical simulations: Bromm & Loeb 2002

  17. Supermassive Stars For a spherical (non-rotating) star: general-relativistic instability at Angular momentum mass shedding along equator Collapse to a black hole is inevitable for S. Shapiro, et al. 2003 High spin disks: Loeb & Rasio 93; Low-spin disks: Eisenstein & Loeb 95

  18. Growth of Supermassive Black Holes

  19. ; Why Are Quasars Short Lived? Because they are suicidal! Principle of Self Regulation:supermassive black holes grow until they release sufficient energy to unbind the gas that feeds them from their host galaxy Implies a correlation between black hole mass and the depth of the gravitational potential well of its host galaxy

  20. Simple physical model: *Each galaxy merger leads to a bright quasar phase during which the black hole grows to a mass and shines at the Eddington limit. The duration of this bright phase is dictated by the dynamical time of the host galactic disk (7% of the total energy release can unbind the disk on its dynamical time). *Merger rate: based on the extended Press-Schechter model in a LCDM cosmology. Quasar Luminosity Function duty cycle ~10 Myr Wyithe & Loeb astro-ph/0304156

  21. Hydrodynamic Simulations of Quasar Feedback Springel, Hernquist, Di Matteo et al. 2005

  22. Hydrodynamic Simulations of Quasar Feedback (Springel, Di Matteo, & Hernquist 2004)

  23. (Springel, Di Matteo, & Hernquist 2004)

  24. How do black holes accrete gas? Stone et al. 2005

  25. What is the accretion rate into SgrA*horizon? Bolometric luminosity: Bondi rate:

  26. Feeding SgrA* with Stellar Winds Emission region: Loeb, astro-ph/0311512

  27. In what form do black holes release accretion energy? • Radiation • Non-relativistic wind • Relativistic particles and magnetized jets • Neutrinos • Gravitational radiation

  28. Injection of Positrons from AGN Jets e+e- jet AGN X-ray cluster Furlanetto& Loeb 2002

  29. Spectrum of Positron Annihilation Line 3-photon decay of Positronium does not smear line due to keV temperature of cluster electrons (direct annihilation more probable) Line signal detectable with INTEGRAL (launched Oct. 2002) and EXIST (space station) for rich X-ray clusters out to 100 Mpc More details: ApJ, 572, 796 (2002)

  30. Black Hole Binaries due to Galaxy Mergers

  31. X-ray Image of a binary black hole system in NGC 6240 10kpc z=0.025 Komossa et al. 2002

  32. Dynamics of black hole binaries wandering R Figure1.ps Numerical experiment: 400,000 stars Typical binaries coalesce in less than 10 Gyr due to wandering Chatterjee, Hernquist, & Loeb 2002

  33. kick velocity from galaxies

  34. Gravitational Wave Amplitude from a Black Hole Binary at z=1

  35. Gravitational Radiation from Coalescence of Massive Black Hole Binaries PULSARS LISA REDSHIFT FREQUENCY (Hz) Wyithe & Loeb 2002

  36. How do nuclear black holes influence the evolution of their host galaxies, X-ray clusters, or the larger-scale intergalactic medium? Fabian et al. 2003 Kraft et al. 2005 McNamara et al. 2005 Forman et al. 2003 What is the dominant mechanism that mediates the energy transfer? acoustic waves, relaticistic particles and magnetic fields Is the growth of the stellar spheroid affected by this feedback?

  37. Correlation between black hole mass and velocity dispersion of host stellar system Tremaine et al. 2002 Ferrarese 2002

  38. halo velocity dispersion dynamical time of galactic disk After translating this relation matches the observed correlation in nearby galaxies (Tremaine et al. 2002; Ferarrese & Merritt 2002) Self-regulation of Supermassive Black Hole Growth quasar galactic disk Silk &Rees 1998; Wyithe & Loeb 2003

  39. Clustering Statistics of Quasars Lines: correlation function of model with (SIS) Data points: 2dF Quasar Survey (Boyle et al. 2000) Wyithe & Loeb 2004; astro-ph/0403714

  40. Data on Quasar Clustering/LF Implies: • Local relation between galactic halo/black-hole + redshift evolution of quasar correlation length are consistent with and not • If mergers trigger quasar activity, then quasar lifetime scales with dynamical time of host galaxy rather than the redshift-independent Salpeter-Eddington time for its growth Wyithe & Loeb 2004; astro-ph/0403714

  41. Effects of Quasars on the Intergalactic Medium: Ionization and Magnetization

  42. The Earliest Quasar Detected:z=6.4 Fan et al. 2002

  43. Cosmic Hydrogen was significantly Neutral at z~6.3 Ionization(Stromgren) sphere of quasar Size of HII region depends on neutral fraction of IGM prior to quasar activity and quasar age line of sight R(t) Wyithe & Loeb, Nature, 2004; astro-ph/0401188

  44. Cosmic Background Radiation Gamma-ray background

  45. Quasars as Perturbers:Impact of Quasar Outflows on the IGM small-scale structure; magnetization; ionization BAL outflow jet Magnetized bubble Intergalactic Medium (IGM) quasar Is the IGM fully magnetized just like the ISM? Furlanetto & Loeb 2001

  46. Volume Filling Factor of Quasar Bubbles Volume filling factor of IGM Magnetic energy density normalized by thermal at 10^4 K

  47. Probability Distribution of Bubble Radius *Magnetic pressure larger minimum b-parameter of Lya forest

  48. Probability Distribution of Bubble Magnetic Field *Could account for intra-cluster and galactic fields through adiabatic compression. Explains synchrotron halos of clusters.

  49. Key questions • Is general relativity the correct description of strong gravity?Do black holes exist?Are they described by the Kerr metric (with the predicted properties of the event horizon, innermost stable circular orbit, photon orbit, etc.)? • What is the spin and mass distribution of astrophysical black holes? Why? • What is the history of black hole formation and evolution? How did the first black holes form? Was growth dominated by accretion of gas, consumption of stars or mergers? Do binaries coalesce? What is the impact of gravitational-wave recoil? • How do black holes accrete gas? What are the geometry and radiative efficiency of the accretion flow as a function of the accretion rate? Which fraction of the infalling mass is expelled in outflows? • In what form do black holes release accretion energy? What is the relative fraction of radiation, magnetically-dominated outflows, relativistic particles, non-relativistic winds, neutrinos, gravitational waves?How are relativistic jets produced? Are they made of e+e- or baryons? • How do nuclear black holes influence the evolution of their host galaxies, X-ray clusters, or the larger-scale intergalactic medium?What is the origin of the correlations between black hole mass and spheroid properties?What sets the maximum mass of galaxies?

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