Black Holes and Quasars Black Holes
Normal and Super-‐massive The Schwartzchild Radius (event horizon) Normal and Super Massive Black Holes (SMBHs) The GalacAc Centre (GC) The Black Hole in Andromeda
AcAve GalacAc Nuclei (AGN) Discovery of Seyferts and Quasars Basic properAes Blazars, QSOs, BL Lacs, OVVs, LINERs etc. AGN UnificaAon SMBH correlaAons with host galaxy AGN AcAvity with Cosmic Time
ImplicaAons for galaxy formaAon
Black Holes Gravity is the curvature of space-time by matter. If sufficient mass exists
in a small enough volume space-time is distorted such that even light cannot escape
The Schwarzschild Radius • The radius at which even light cannot escape is known as the event
horizon or Schwarzschild radius. • For a non-‐rotaAng black hole this is simply when the KineAc Energy =
GravitaAonal Energy for a photon
2
2
2
22121
cGMr
rGMmmc
rGMmmv
S
S
=
=
=
r s
Types of Black Hole • Normal
– Formed from massive stars going supernovae
• Super-‐massive – Formed in galaxy cores during iniAal collapse?
• Most galaxies are believed to harbour a super-‐massive black-‐hole in their cores – Existence of Intermediate Mass Black Holes uncertain
!MM 10~BH
!" MM 97
BH 10~
Evidence for SMBHs • We find that stars have velociAes of >110km/s within 2.5pc of
the core of M31
Super-massive BH in M31 • IF they are in circular orbits we can use the Virial theorem to
calculate the mass inside r
• In our Milky Way galaxy – Velocities > 1000 km/s inside 0.01 pc!
• => 2 x 106 Msun SMBH
!
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MM
M
637CORE
11
16232
CORE
108.6104.11067.6
1035.2)10110(
kgGrv
Our Galactic Centre
Infrared Studies • Infrared (2 µm) penetrates through the dust • Can use to probe stellar populaAons and dynamics in GC • Find central cluster of young massive stars
– Teff ~ 20,000 K – Burst of star formaAon 107 years ago?
• Or masses modified by star-‐star collisions? – Plus repeated bursts in the past (AGB stars present) – Stellar density ~> 106 stars pc–3 – Compare solar neighbourhood: stellar density ~ 0.1 stars pc–3
– Use stars to study kinemaAcs – And mass of central object
GRvM
RGMv
22 =!=
Time lapse movie of Galactic Centre over past 12 years
Orbital Motions
Proper Motions in Galactic Centre • Measured by speckle and (now) adapAve opAcs
– In IR (2.2 mm) to see through dust
• Speckle: many short exposures – Freeze out effects of turbulence in atmosphere – Add coherently to see image!
• Measures velociAes of many stars near GN • From velociAes: mass
– At 0.01 pc: v ~ 1000 km/s – At 0.04 pc: v ~ 500 km/s
• ImplicaAon:
( ) constant 5.0constant 2 !<"! pcrMRv
Obs.Tech.
i.e., Keplerian
Central Black Hole • Mass of central object
• Mass within 0.01 pc is ~3 x 106 Msun • Keplerian velociAes inside of 0.5 pc
• Mass within 10 pc is ~3 x 107 Msun • mass density is ~4 x 106 Msun pc-‐3
• So, does this necessarily mean a black hole? • If not, mass density is ~4 x 1012 Msun pc-‐3
– Cluster of neutron stars?
GRvM2
=
Mass distribution
106
mass
107
105
Radius (pc)
0.01 0.1 1.0 10.0
Msun
4 x 106 Msun pc-3 4 x 1012 Msun pc-3
3 x 106 Msun
Sgr A* • Radio source in centre of nucleus • Molecular gas disc rotates around it • Stellar cluster centred on it • What is it?
– Variable non-‐thermal radio source – Luminosity < 105 Lsun
• Size: 0.3 mas ~ 2.4 AU!!! • Could be a neutron star • But it doesn’t move!!! Should be in equilibrium with stellar
cluster! v < 200 km/s – Most probably a black hole – Schwarschild radius ~ ~ few Rsun
R = GMc2
Flare from black hole • x-‐ray flare from central locaAon
• Due to mass falling into the GC super-‐massive black hole
• Heats up and emits in X-‐rays before crossing ‘event-‐horizon’
Galaxies – AS 3011 16
Quasars & Seyferts
• 1943 Carl Seyfert publishes a list of odd galaxies: – Mostly spirals with point-‐like nuclei – Broad emission lines – Also high ionisaAon states (O[VI]) – Doppler interpretaAon implied >1000 km/s
• Later two classes of Seyferts proposed: – Seyfert Is: Broad hydrogen lines, narrow forbidden lines (e.g., O[III]) – Seyfert IIs: Only narrow lines present
• Assumed lines originate from disAnct regions: – Broad lines from Broad Line Region – Narrow lines from Narrow Line Region
Galaxies – AS 3011 17
NGC5548 (Seyfert I) NGC3277 (Normal Spiral)
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Seyfert 1 showing both Broad and Narrow line features
Seyfert 2 showing narrow lines only
Images of both show a spiral galaxy with a very bright central
nucleus
Galaxies – AS 3011 19
Discovery of Quasars -‐ Strong radio sources known to correlate with point-‐like objects -‐ Maarten Schmidt collected the first spectrum for radius source 3C273 -‐ Contained unexplained broad lines, idenAfied as redshited hydrogen -‐ Eventually deduced a redshit of 0.16 (Schmidt, Nature, 1963) -‐ Soon other Quasars were discovered with redhists upto 2 -‐ Current record holder around z=6.0
Galaxies – AS 3011 20
OpAcal jet
3C273
Typical Quasar or QSO spectrum
Steep conAnuum Broad lines No discernable host galaxy
point-‐like.
Galaxies – AS 3011 22
ObservaAons -‐> ProperAes Point-‐like = compact Distant = luminous Broad lines = high velociAes High excitaAon lines = energeAc Variable = small (<1 lyr)
Galaxies – AS 3011 23
at 1 Gpc
Oten have associated jets visible in raAo due to relaAvisAc charged material zipping out along open field lines: Synchrotron radiaAon Jets oten extend 10-‐500kpc!
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Emit over all wavelengths:, e.g.,Mk421
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Other AGN types Quasars, radio-‐loud QSO (Quasi-‐stellar objects), radio quiet Seyfert I(Broad lines) Seyfert II(Narrow lines) Blazers (Highly variable systems), superluminous
- BL Lacs (BL Lacertae)=no features - OVV (OpAcally violently variable)
LINERS - Weak Seyferts (no broad lines)
Galaxies – AS 3011 26
Theories Two compeAng theories:
- Nuclear starbursts - Super-‐massive black holes
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Evidence for black holes • Gas moving at ~10,000 km/s, inconsistent with stellar orbits • Emission lines change in brightness over days to weeks
– light travel Ame implies emission from region only ~ light-‐weeks across (~0.01 pc)
• Hence must have very high density, because – fast orbits within very small region: vorbit ~ (G M / r)1/2
• Only a black hole can pack this much maver in so densely – the power is generated at a few Schwartzschild radii RS = 2 G Mbh / c2 (≈ 3 km x Mbh / Msolar)
• However SMBHs as central mechanism only adopted following discovery of the GC SMBH and that in M31 and M84 which also exhibits a jet
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unified model
• The several types may be the same kind of object seen from different angles (Unified Model) – see narrower lines if a spectrum comes from gas orbiAng further out – fastest stuff is in an accreAon disk around the black hole
(not to scale!)
see Seyfert 1
see Seyfert 2
narrow line region clouds at ~0.1-‐1 kpc
broad line region
accreAon torus
can also see polarized light from near the nucleus if scavered
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AGN Unification
Seyfert 2 galaxy
Seyfert 1 galaxy
Quasar Blazar
Jet !!!
Torus
Antonucci, 1993
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CorrelaAon between SMBH mass and bulge velocity dispersion
CorrelaAon between SMBH mass and Bulge Absolute magnitude
AGN acAvity much more common in the past. Consistent with bulge formaAon preceeding disc formaAon
AGN ac+vity
The Cosmic Star-‐formaAon History
Constructed from measurements of Hα or UV fluxes at various redshits
CSFH v AGN AcAvity
AGN acAvity does not seem to trace SFH at high-‐z 1. Data uncertain 2. Redshit axis misleading
…..lets switch to Ame à
CSFH v AGN acAvity v Time
.
.
.
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Puxng it together ? Dark Maver Baryonic Maver 0yrs 5Gyrs
13Gyrs
Rapid merging
Slow merging
SMBHs AGN
BULG
ES
DISKS
P-‐BU
LGES
??
COLLAPSE/MERGERS
INFALL
SECULAR
ACCE
LERA
TING DEC
ELER
ATING
U
AGN acAvity
AGN no longer acAve