christopher | vlad | david | nino supermassive black holes

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  • Slide 1
  • Christopher | Vlad | David | Nino SUPERMASSIVE BLACK HOLES
  • Slide 2
  • WHAT IS A BLACK HOLE? Massive object from which nothing can escape. Even light is attracted by gravity. Schwarzschild radius is the distance for a given mass where the escape velocity is the speed of light A black hole has its entire mass enclosed in its own Schwarzschild radius.
  • Slide 3
  • HOW CAN WE SEE BLACK HOLES? No light escapes Hawking Radiation Not observed Accretion disks Observed radiation An artist's rendering of the Cygnus X-1 system. (from http://spaceart1.ning.com/photo/cygnus-x1)
  • Slide 4
  • HOW DO BLACK HOLES FORM? Type II Supernova of a massive star Collapse of a neutron star Nothing can stop it Dont know what happens after
  • Slide 5
  • HOW DO WE WEIGH BLACK HOLES? Mass can be inferred from orbital velocities of stars around it The position of a star around the Supermassive Black Hole Sgr A* (from http://www.sciencemag.org)
  • Slide 6
  • PROPERTIES OF SUPERMASSIVE BLACK HOLES Masses range from millions to billions of solar masses Located at center of most galaxies Especially flat, normal galaxies with bulge component Active SMBHs emit energetic jets X-Rays and Gamma rays Perpendicular to accretion disks (possibly) along rotation axis Limit star growth by clearing gas along their axis
  • Slide 7
  • PROPERTIES OF SUPERMASSIVE BLACK HOLES Strong X-Ray emitters Account for half of radiation after Big Bang SMBH rotation drags spacetime in direction of rotation (Roy Kerr) frame dragging Local phenomenon Can delay matter falling in due to sideways motion Weaker tidal forces than BH of regular size/mass Since larger surface area of event horizon
  • Slide 8
  • EATING OR FASTING? DIFFERENT FACES OF SMBHS SMBHs may regulate galactic growth along with appetite for matter Saggitarius A* - dormant SMBH in Milky Way nearly empty Very little matter in immediate surroundings Large amounts of matter in surroundings Quasar galaxies, Seyfert galaxies, Blazar galaxies Quasar galaxy Most variably-luminous objects in universe (> 10 12 L solar ) Powerful jets powered by accretion disk around SMBH Central SMBH 10,000x times regular black hole 3C 273 first quasar discovered early 1960s Quasar activity peaked in early universe
  • Slide 9
  • EATING OR FASTING? DIFFERENT FACES OF SMBH Seyfert galaxy Produce spectral emissions from highly ionized gas Large amounts of IR, UV, X-Ray rad. Jet velocity 500-4,000 km/s Central SMBH mass 10 8 M solar Blazar galaxy Emission jets pointed towards Earth Radiation spectrum radio to Gamma rays Variable / Unstable output At 9 billion ly can be detected with Earthly instruments SMBHs key for early universe Facilitate formation of galaxies
  • Slide 10
  • WHY DO WE THINK THEY ARE BLACK HOLES? Sphere of influence r h ~ GM BH / 2 ~ 11.2(M BH /10 8 M S )/( /200kms -1 ) 2 pc Keplerian velocity distribution near galactic center Must be highly concentrated mass at center Proper motion of stars in Milky way indicate singularity at galactic center Called Sagittarius A* Higher concentration than normal of 22Ghz water masers imply an AGN in NGC 4258
  • Slide 11
  • OTHER METHODS Hubble Space Telescope high resolution images Shows clearly gas or stellar dynamics at galactic nucleus Only works if gravity is most influential force on gas Reverberation or Echo mapping Only for type 1 active galactic nuclei Can probe regions up to 1000 times the Schwarzschild Radius
  • Slide 12
  • HOW DOES THE SMBH RELATE TO THE SURROUNDING GALAXY? M BH vs. blue luminosity of the bulge (whole galaxy if elliptical) Correlates to blue luminosity from the bulge Generally scattered correlation; less so for ellipticals Latest relation given by log(M BH ) = (8.370.11) (0.4190.085)(B 0 T + 20.0) M BH vs. velocity dispersion, () relates to L B, which relates to M BH Tighter correlation than mass vs. bulge light; maybe more fundamental Latest relation (M BH /10 8 M Sun ) = (1.660.24)(/200km s -1 ) 4.680.43
  • Slide 13
  • OTHER CORRELATIONS WITH HOST GALAXY M BH vs. bulge light concentration (C) Tight correlation; little scattering Practical relation; needs only one measurement Depends on parametric characterization of light profile M BH vs. Dark Matter Halo correlates tightly with large scale circular velocity distribution Less massive halos are less efficient at forming SMBH (M BH /10 8 M Sun ) ~ 0.10(M DM /10 12 M Sun ) 1.65
  • Slide 14
  • HOW DO SUPERMASSIVE BLACK HOLES FORM? What came first? Supermassive Black Holes or galaxies ? Proponents of galalxies first: Observed galaxies without SMBH (ex. NGC 2613) Bulge component in flattened normal galaxies necessary
  • Slide 15
  • Proponents of SMBH first: Uniform density shown by microwave background radiation Not sufficiently clumped to form SMBH from regular matter alone Suggest SMBH from dark matter Quasar activity peaked 10 billion years ago Primordial seed theory Central black hole can double its mass every 40 million years
  • Slide 16
  • GROWTH OF SUPERMASSIVE BLACK HOLES Stellar and intermediate mass black holes gravitate towards galactic center Coalesce there to SMBH (ex. NGC 253) Major growth from galactic collisions and mergers Example collision of Milky Way with Andromeda in 5 billion years New Black Hole: 100 million M solar Both from SMBH mergers and influx of material
  • Slide 17
  • Slide 18
  • WILL SUPERMASSIVE BLACK HOLES DIE? Will stop growing Estimated terminal mass 1-10 billion M solar Hawking radiation 30 M solar black hole 10 61 times current age of universe 100 billion M solar black hole 10 98 years