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  • Black Holes In AstronomyBlack Holes In Astronomy

    credit: NASA

  • Black holes turn our intuition upside-down! But first, a bit of history

    Einstein 1915: established equations describing how matter curves space and warps time

    Karl Schwarzschild 1916: found the simplest, spherically-symmetric space-time map

  • Physics of an accreting Black Hole

    horizon

    static limit

    ergosphere

  • Physics of an accreting Black Hole

    horizon

    static limit

    ergosphere

    radiation

    magnetic fields

    jet

    jet

  • Black-hole accretion simulation

    McKinney & Gammie 06 McKinney & Gammie 06McKinney & Gammie 06

  • Making black holes from massive stars

    • Mass > 25 Solar • Lives < 10 million years • Ends life with gravitational collapse forming a black hole

    60 km

    Stellar-mass black hole (a few times more massive then the Sun)

  • credit: NASA

    • Stellar-mass black holes are “seen” only if they have a close stellar companion

    • What’s observed is a very hot accretion disc

    • The mass can be measured from the companion’s motion

    Stellar-mass black holes

  • Supermassive black holesSupermassive Black Holes

  • Historical timeline:

    1962. Quasars discovered at billions of light years by Schmidt.

    1964. Zeldovich & Novikov and Salpeter argue that Quasars are powered by the accretion of gas onto supermassive black holes

    1969. Lynden-Bell argues that supermassive black holes should exist at the centers of many galaxies.

    1996+. Hubble Telescope observations, analyzed using Martin Schwarzschild’s method, establish that supermassive black holes exist in the large majority of galaxies with a central bulge.

  • Click to edit Master text styles Second level

    Third level Fourth level

    Fifth level

    Jets and lobes of Cygnus A

    Carilli et al.

    Supermassive black holes are the most powerful engines in the Universe

  • Jet-driven bubbles Click to edit Master text styles

    Second level Third level

    Fourth level Fifth level

    Allen et al. 06

  • Supermassive black holes

  • Relationship between SBHs and host galaxies

    Black-hole mass

    galactic velocity dispersion

    Gebhard et al, 00 Ferrarese & Merritt 00 Tremaine et al. 02

  • Main question: how do SBHs form and grow to current large masses (0.1 million to 10 billion solar)?

    Observational answer: SBH grow from smaller seeds and acquire most of their mass by gas accretion.

    1. Observe light from systems with SBH accretion (quasars and active nuclei) 2. Divide by 0.3c to obtain mass 3. Compare with SBH mass density in the local Universe

    2

    Good agreement! Soltan 1982 Yu & Tremaine 2002

  • Andrea Ghez, UCLA

    Keck telescope, Hawaii

    Black hole at the center of our Galaxy, the Milky Way.

    European Southern Observatory VLT, Chile

    Reinhard Genzel, MPE

    Reinhard Genzel, MPE

    Andrea Ghez, UCLA

    Keck telescope, Hawaii

    Supermassive Black Hole at the center of our Galaxy, the Milky Way

    European Southern Observatory VLT, Chile

  • Keck Stellar Orbits.

  • VLT stellar orbits (reconstructed in 3 dimensions), of stars moving around the 4 million solar masses Supermassive Black Hole, SgrA*.

  • Do black holes ever find partners?

  • Stellar-mass black hole binaries

    or

    Marriage by attraction

    Arranged marriage

  • LIGO: will measure stellar-mass BH mergers

    LIGO: will measure stellar-mass BH mergers

  • Hubble Komossa et al 02 (Chandra)

    Merging Galaxies Merging Supermassive black holes?

    Supermassive black hole binaries

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  • Black holes have no hair!

    4 million solar mass, spin 0.6, BH is looking for other BH.

    You know what we do.

  • Dance and merger of black holes Caltech+ CornellDance and merger of black holes

    credit: Caltech+Cornell

  • Binary with spinBinary without spin

    Eccentric inspiral

    Circular inspiral Scott Hughes, MIT

    “Listening” to gravitational waves from black-hole mergers

  • Hubble Komossa et al 02 (Chandra)

    Merging Galaxies Merging Supermassive black holes?

    Supermassive black hole binaries

  • Theorists dream of mergers: Begelman, Blandford, &Rees 1982:

    10 kpc 2pc 1pc 0.01pc merger

    Dynamical friction

    scattering wishful thinking

    gravitational waves

    gas non-spherical potential

    Another black hole

  • Orbital evolution: the chirp – see first lecture!

  • Population of chirping sources Amount of time spent near frequency f

    Number of sources in the frequency band df scales with dt

    Power spectrum from incoherent superposition

    Characteristic strain

    GR prediction!!

  • Gravitational waves: a (Gaussian, stochastic) background!

    Phinney 01 Jaffe & Backer 03 Wyithe & Loeb 03 Sesana et al. 07, 08, 09 Ravi et al. 12

    Click to edit Master text styles Second level

    Third level Fourth level

    Fifth level

    amplitude spectral index

    General Relativity prediction:

  • Conclusions

    • Black holes are the most powerful engines in the Universe. They power quasars, active galactic nuclei, and (probably) gamma-ray bursts

    • Binary black-hole astrophysics is on almost solid ground – very good arguments for why GW are there in the PTA band

    Slide 1 Slide 2 Slide 3 Slide 4 Black-hole accretion simulation Making black holes from massive stars Slide 7 Supermassive black holes Slide 9 Slide 10 Slide 11 Supermassive black holes Slide 13 Slide 14 Slide 15 Slide 16 Slide 17 Slide 18 Stellar-mass black hole binaries LIGO: will measure stellar-mass BH mergers Slide 21 Slide 22 Black holes have no hair! Dance and merger of black holes Slide 25 Slide 26 Slide 27 Slide 28 Population of chirping sources Slide 30 Conclusions