Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
ASTROPHYSICAL BLACK HOLES
Andy Fabian
Institute of Astronomy
University of Cambridge
Introduction
AGN Feedback
How quasars work
JOHN MICHELL ~1784
• SUN’s escape velocity is 600 km/s
• Velocity of light is 300,000 km/s
• Escape velocity from 108 Suns stacked together = velocity of light
• HOW COULD WE SEE SUCH AN OBJECT?
ALBERT EINSTEIN
GRAVITATIONAL LIGHT BENDING
GPS GR=45microsec/day (or ~10km/day)
BLACK HOLES
Karl Schwarzschild Roy Kerr
Astrophysical Black Holes have only
MASS and SPIN
Astrophysical Black Holes have only
MASS and SPIN
Event horizon radius is 3 km per Solar mass
How to find a black hole
Large mass in small radius Earth mass in 1cm;
Sun’s mass within 15km;
Billion solar masses within orbit of Uranus
How to find a black hole
Large mass in small radius Earth mass in 1cm;
Sun’s mass within 15km;
Billion solar masses within orbit of Uranus
Large luminosity varying rapidly Million solar luminosities in a few millisec
Billion solar luminosities in a few minutes
Trillion Solar luminosities in a few days
Munich (Genzel) and Los Angeles (Ghez) groups agree
Black Hole
Mass
Galaxy Mass
AGN Feedback
2
2
1.0
005.0
McE
McE
Nuclear fusion
Black Hole Accretion
211105 McE TNT
2
2
1.0
005.0
McE
McE
Nuclear fusion
Black Hole Accretion
211105 McE TNT
100 million
20
Possible effect of central black hole on galaxy
• Mass of BH ~M/1000 • Energy released during growth of BH
EBH~0.1MBHc2~10-4Mc2
• Energy required to disperse galaxy~Mv2
• Therefore Egal/EBH~104(v/c)2
• Since v<c/1000, Egal~0.01EBH
• Conclude that BH can destroy galaxy
Possible effect of central black hole on galaxy
EBlackHole >100´EGalaxy
Energy released by growth of Black Hole
Gravitational Energy of Host Galaxy
Chandra
1.4 Ms
900ks Chandra image of Perseus
cluster
Pressure map of the Perseus cluster
Radio source
1 arcmin
22 kpc
Ripples in surface
brightness –
sound waves
1 arcmin
22 kpc
Mrk 231
Elliptical galaxies are now red and dead
Evolution of quasars
You are here Big Bang
Ion tail
Dust tail
<- to Sun
Effects of radiation pressure and winds
Galaxy luminosity
log
Number density
of galaxies
Log Luminosity/Mass
AGN Feedback
Halo mass
AGN Feedback
Occurs through
•Jets
•Winds
•Radiation Pressure
Fabian 2012 ARAA
The accreting black hole
• How quasars work
• Gravitational energy released
within ~15 rg
To observer Direct Power-law
Accretion disc
(Quasi-blackbody in optical/UV for AGN,
soft X-rays for stellar mass BH)
Rapid variability in AGN
MCG-6-30-15
To observer Direct Power-law
“Reflection” spectrum
Accretion disc
Ross+Fabian93,05
Schwarzschild
Kerr
Fabian+89, Laor 91…
Gravitational
redshift
Reflection in accreting BH
Add relativistic
blurring
Soft excess – broad iron line – Compton hump
Reflection spectrum
Reflection in accreting BH
Add relativistic
blurring
Soft excess – broad iron line – Compton hump
Reflection spectrum
NUSTAR
Risaliti+13
Suaksu
Very Broad Line Spinning BH
Strength of line relative to continuum determines light bending
Gravitational
redshift
Suzaku Miniutti+07
SPIN
C. Reynolds13
AGN Spin Census
To observer Direct Power-law
“Reflection” spectrum
Accretion disc
Path difference leads to reverberation
1H0707-495
Gallo+04
Broad iron-L and iron-K emission lines
Fabian+09
Broad iron-L and iron-K emission lines (XMM)
Reflection
dominated
Power-law
dominated
0.3 keV vs 1-3 keV
Rapid variations
(< 15 min)
Powerlaw leads
reflection:
Reverberation
1H0707-495
Understanding the origin of the hard lags
Kara et al 2013a
Kara+13a
High frequency lags have reflection spectrum
De Marco+13
Soft lags are common and require
emission + reflection from within
few rg
2D transfer function
h = 10 RG, i = 45 deg,
a = max
Cackett13
Cackett13
Dan Wilkins thesis
The FUTURE
Galactic Centre – G2 cloud, shadow image
M87 – shadow image, jet acceleration zone
AGN Feedback – ALMA, JWST etc
X-rays - ASTRO-H
Summary
• Supermassive BH common in the Universe, lying at the centre of most galaxies
• Appear to play a key role in the evolution of galaxies, terminating their growth. Influence extends over 1010 in radius
• Also many stellar mass BH in each galaxy
ALMA
Event Horizon
Telescope
ASTRO-H
Continuum variation seen first
then red wing
finally blue horn
(not to scale)
Energy dependence of reflection lag
NGC 4151 Red wing responds faster and to higher
frequencies than blue horn
Energy (keV)
High freq
5x10-5 < f < 50x10-5 Hz
Low freq
f < 2x10-5 Hz
Zoghbi+12
Predicted Spin Distribution Berti+Volonteri08
Mergers
Accretion
Chaotic accretion
Spin • Cosmic black holes defined just by mass
and spin
• Spin established at birth for stellar mass BH
• Depends on accretion and merger history for AGN
• Spin of accreting black holes is measurable if Innermost Stable Circular Orbit, ISCO, can be identified
• Accretion efficiency depends on spin
• Maximum gravitational redshift depends on spin
a* =cJ
GM 2
Assumption: measurements of rISCO determine a
Conserve energy
ULAS1234
Size
Mass 1.5<z<2.5
Spectrum of these filaments is unlike anything in our Galaxy,
other than Crab
and due to energetic particles (the hot gas?)