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?)