Supermassive Black Holes

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Supermassive Black Holes

Leiden, Modern Research: Galaxy Formation and Evolution Tom van Leth & Maarten van Dijk

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Introduction

• Introduction

• Black hole theory

• Characteristics of SMBH

• Identifying SMBH

• SMBH growth and galaxy evolution

• SMBH in our own galaxy

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Quasi-Stellar Radio Sources

•1950: First quasar detected

•Radio sources without any visible lightsource

•Antimatter?

•1963: Breakthrough

•First sign of a supermassive black hole (SMBH)

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Black Holes: The theory

•The basics:

•Star collapse

•Schwarzschild Radius

•Light cannot escape the hole

•Then how can we see them?

A black hole: an artist’s impression

http://heac.albanova.se/research/

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Black holes and their disc

• Gravitational potential energy

• Conversion to kinetic energy (speed and temperature)

• Accreting mass forms a disc (preservation of angular momentum)

• Black holes don’t glow, their disk does

• Bremsstrahlung (translated: deceleration radiation)

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Bremsstrahlung

• Electron passes a charged particle

• Emits some energy as a photon (not necessarily X-ray)

• This is (indirectly) the light from black holes

• Effectivity of this radiation

is high: up to 10% Bremsstrahlung

http://surf.agri.ch/wuelfert/lecture/physics/imaging/XR/imag_xr_images/XR_bremsst.gif

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Big Brother: the characteristics

• Supermassive Black Holes range from

• Found in the centres of galaxies

• Most of the galaxy doesn’t even notice the SMBH

• Only near the nucleus, where the combined mass in stars is smaller than the mass of the SMBH does it dominate local gravity

e

6 9

10 -10 M

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Identifying SMBH

• Finding out something is a BH or a SMBH is hard even if it emitted light, since its too small.

• Even the SMBH in M31 is too small. Hubble Space

telescope has a resolution of 0.1 arcsec. But the SMBH has a size of arcsec.

• Local density is hard to explain with a non-BH theory

8 * 10−7

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Identifying SMBH – Are there

alternatives?

• The most plausible BH alternatives are clusters of dark objects produced by ordinary stellar evolution

• Dense dark star cluster – brown dwarfs

• Fermion Balls: Concentrated regions of low mass non- interacting particles (dark matter?)

• Basically, a BH or SMBH is the best guess, since other scenario’s are incapable of explaining the

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Evolution of galactic black holes

• Relation between black holes and formation of galaxies

• Different scenarios

• Quasars are nuclear black holes accreting much matter in a short time

• Most of the mass accreted in “quasar era” (redshift 2-3)

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Relations for black hole mass

•Black hole mass – bulge luminosity

•Black hole mass – bulge velocity dispersion

•No relation with disc of galaxy

•Black hole growth caused by galaxy mergers

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Black holes and dark matter

•Quasars appear quite early (z=5)

•Dark matter halos around quasars

•Black hole mass – halo mass relation

•“Accretion shock” predicted

•Evidence: Spectrums of quasars

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Black holes and star formation

• Simulations on galaxies

• Black hole growth and star formation triggered by mergers

• With black hole: rapid star formation and halt in star formation

• Without: steady rate of star formation

• More massive black holes Æ shorter lived quasars

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The black hole in the center of our

galaxy

• Sagittarius A

• Mass determination using orbiting stars

• Near infrared flares 3 . 7 1 0 6

M = ⋅ M _e

17 r ≤ lh

http://www.eso.org/outreach/press-rel/pr-2002/phot-23a-02-normal.jpg

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The black hole in the center of the

galaxy

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Why is the black hole in our

galaxy so dim?

• Fuel is almost depleted

• Accretion is less efficient

• Gas is ejected from black hole

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Summary

• Black holes

• SMBH Characteristics

• Means to identify a SMBH

• SMBHs and galaxy mergers, star formation and dark matter

• Our own SMBH

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References

• SOurces: http://chandra.as.utexas.edu/~kormendy/bhsearch.html

• Nature, 30 october 2003, p.934, near infrared flares from accreting gas around the supermassive black hole at the galactic center

• Nature, 23 january 2003, p.329, feeding the first quasars Nature, 30 october 2003, p.425, sparks of interest

• Nature, 17 october 2002, p.694, a star in a 15.3-year orbit around the supermassive black hole at the centre of the milky way

• Nature, 10 february 2005, p.604, Energy input from quasars regulates the growth and activity of black holes and their host galaxies

• http://64.233.183.104/search?q=cache:FOizrt-

• www.physics.ucsb.edu/~blaes/amaldi.ps+SMBH+alternatives&hl=nl

• http://cassfos02.ucsd.edu/public/tutorial/Quasars.html

• http://en.wikipedia.org/wiki/Quasar#History_of_quasar_observation

• http://www.universetoday.com/am/publish/early_black_holes_grew_quickly.html?1762005

• http://en.wikipedia.org/

• Science, 11 june 2004, p. 1581, Giant Black Holes Shed Their dusty Veils

• Science, 20 june 2004, p. 1898, Evidence for Black Holes

• Science, 2 may 2003, p. 752, Black Holes at the Cosmic Dawn

• Science, 2 January 2005, p. 77, Black Hole Accretion

• http://www.mpe.mpg.de/ir/GC/index.php

• arXiv:astro-ph/0103466 v1 28 Mar 2001, The motion of stars near the Galactic center: A comparison of the black hole and fermion ball scenarios

• MNRAS, Submitted 2005 October, Constraints on Alternatives to Supermassive Black Holes