M87 Hercules A radio jets Active Galactic Nuclei AGNs and Supermassive Black Holes The identification by Maarten Schmidt 1963 Nature 197 1040 of the radio source 3C 273 as a star ID: 459878
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Slide1
Active Galactic Nuclei (AGNs) and Supermassive Black Holes
M87Slide2
Hercules A radio jets
Active Galactic Nuclei (AGNs) and Supermassive Black HolesSlide3
The identification by Maarten Schmidt (1963,
Nature
, 197, 1040) of the radio source 3C 273 as a
“
star
”
with a redshift of 16 % of the speed of light came as a huge shock. The Hubble law of the expansion of the Universe implied that 3C 273 was second-most-distant object known. It must be enormously luminous — more luminous than any galaxy.
The energy requirements for powering quasars were the first compelling argument for black hole engines.
The Discovery of Quasars
3C 273Slide4
The Discovery of Quasars
3C 273
The identification by Maarten Schmidt (1963,
Nature
, 197, 1040) of the radio source 3C 273 as a
“
star
”
with a redshift of 16 % of the speed of light came as a huge shock. The Hubble law of the expansion of the Universe implied that 3C 273 was second-most-distant object known. It must be enormously luminous — more luminous than any galaxy.
The energy requirements for powering quasars
were the first compelling argument for black hole engines.Slide5
Many radio galaxies and quasars have jets
that feed lobes of radio emission
Cygnus ASlide6
Supermassive Black Holes as Quasar Engines
Let
’
s try to explain quasars using nuclear reactions like those that power stars:
The total energy output from a quasar is at least the energy stored in its radio halo ≈ 10
54
Joule.
Via E = mc
2
, this energy
“weighs” 10 million Suns
. But nuclear reactions have an efficiency of only 1 %. So the waste mass left behind in powering a quasar is 10 million Suns / 1 % ≈ 1 billion Suns. Rapid brightness variations show that a typical quasar is no bigger than our Solar System. But the gravitational energy of 1 billion Suns
compressed inside
the Solar System
≈ 10
55
Joule.
“
Evidently, although our aim was to produce a model based on nuclear fuel,
we have ended up with a model which has produced more than enough energy
by gravitational contraction.
The nuclear fuel is irrelevant.
”
Donald Lynden-Bell (1969)
This argument convinced many people that quasar engines are
supermassive black holes that swallow surrounding gas and stars.Slide7
Why Jets Imply Black Holes — 1
Jets remember ejection directions for a long time.
This argues against energy sources based on many objects (supernovae).
It suggests that the engines are rotating gyroscopes - rotating black holes.
HSTSlide8
Why Jets Imply Black Holes — 2
Jet knots move at almost the speed of light.
This implies that their engines are as small as black holes.
This is the cleanest evidence that quasar engines are black holes.
HSTSlide9
Why Jets Imply Black Holes — 2
Jet knots in M
87 look like they are moving at 6 times the speed of light
(24 light years in 4 years).
This means that they really move at more than 98 % of the speed of light.
HST
Biretta et al. 1999Slide10
Supermassive Black Holes as Quasar Engines
The huge luminosities and tiny sizes of quasars can be understood if they are powered by black holes with masses of a million to a few billion Suns
.
Gas near the black hole settles into a hot disk, releasing gravitational energy as it spirals into the hole.
Magnetic fields eject jets along the black hole rotation axis.Slide11
People believe the black hole picture.
They have done an enormous amount of work based on it.
But for many years there was no direct evidence that supermassive black holes exist.
So the search for supermassive black holes became a very hot subject.
Danger:
It is easy to believe that we have proved what we expect to find. So the standard of proof is very high.
PROBLEMSlide12
Schmidt, Schneider & Gunn 1991, in The Space Distribution of Quasars (ASP), 109
The Quasar Era Was More Than 10 Billion Years Ago
Quasars were once so numerous that most big galaxies had one.
Since almost all quasars have now switched off, dead quasar engines should be hiding
in many nearby galaxies.
NowSlide13
A black hole lights up as a quasar
when it is fed gas and stars.Slide14
Canada-France-Hawaii-TelescopeSlide15Slide16Slide17
The Search For Supermassive Black HolesSlide18
M
31: Black Hole Mass = 100 Million Suns
M
31 on spectrograph slit
Spectrum of M
31 The brightness variation of the galaxy has been divided out. The zigzag in the lines is the signature of the rapidly rotating nucleus and central black hole.
Red Blue
Position along slitSlide19
Kormendy & Bender 1999, ApJ, 522, 772
distance
from center (arcseconds)
rotation speed (km/s)
random speed (km/s)
M
31:
M
= 1.4 x 10
8
M
Slide20
1984 - 1994: analytic V(r),
(r);
isotropy assumed
1988 - 1994: spherical
maximum entropy
Schwarzschild models + flattening
corrections
1994 - 1998: f(E,L
z) models1998 - present: 3-integral Schwarzschild
models
Meanwhile: resolution improved;
analysis of LOSVD was added; two-dimensional kinematic data.M (106 M)
M
(10
6
M
)
r
cusp
/
,
eff
M
32 BH Mass: Publication Date
History of the stellar-dynamical BH search as seen through work on M32:Slide21
Galaxies do not use
their freedom to
indulge in perverse
orbit structure.
M
(10
6 M)M
(106 M)
rcusp /
,eff M 32 BH Mass: Publication DateDerived BH masses have remained remarkably stable despite dramatic improvements
in spatial resolution,data analysis, and modeling techniques.Slide22
The Nuker Team
Additional Nukers:
Gary Bower
Carl Grillmair
Luis Ho
John Magorrian
Jason Pinkney
Christos SiopisKayhan Gultekin
Doug Richstone
Karl Gebhardt
Tod Lauer
Ralf Bender
Sandra Faber
Scott Tremaine
Alex Filippenko
John Kormendy
Richard Green
Alan DresslerSlide23
Martin Schwarzschild
’
s (1979, ApJ, 232, 236) Method:
Orbit Superposition Models
1 -- Assume that volume brightness distrib.
stellar density
gravitational potential.2 -- Calculate “all” relevant orbits in this potential and their time-averaged density distrib.
3 -- Make a linear combination of the orbits that fits surface brightnesses and velocities.
Doug Richstone
Karl Gebhardt
Scott TremaineSlide24
The bulgeless galaxy M
33 does not contain a black hole.Slide25
Typical stars in the nucleus of M
33 have
= 20 ± 1
km/s.
Any black hole must be less massive than 1500 Suns
.Slide26
Black Hole Conclusions
Black hole masses are just right to explain the energy output of quasars.Slide27
Gültekin & Nukers 2009
log M
BH
/ M
log L
V
/ L
σ
/ (km/s)9.0 9.5 10.0 10.5 11.0 60 80 100 200 300 400
9
8
76
log M
BH
/ M
9
8
7
6
This state of the art effective Gültekin et nuk. (2009) is where I will start my
Exgal colloquium on Thursday.
Gültekin et nuk. 2009
Gültekin et nuk. 2009Slide28
CONCLUSION
The formation of bulges
and
the growth of their black holes,
when they shone like quasars,
happened together.Slide29
This unifies
two major areas of
extragalactic research:
quasars
and
galaxy formation.
Hubble Deep Field