Black Holes and Quasars Black Holes Normal and Super-massive The Schwartzchild Radius (event horizon) Normal and Super Massive Black Holes (SMBHs) The Galac c Centre (GC) The Black Hole in Andromeda Ac ve Galac c Nuclei (AGN) Discovery of Seyferts and Quasars Basic proper es Blazars, QSOs, BL Lacs, OVVs, LINERs etc. AGN Unifica on SMBH correla ons with host galaxy AGN Ac vity with Cosmic Time Implica ons for galaxy forma on
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-rota ng black hole this is simply when the Kine c Energy = Gravita onal Energy for a photon
1 GMm mv2 = 2 r 1 GMm mc2 = 2 rS 2GM rS = 2 r s c Types of Black Hole
• Normal – Formed from massive stars going supernovae
MBH ~ 10M! • Super-massive – Formed in galaxy cores during ini al collapse?
7"9 MBH ~ 10 M! • Most galaxies are believed to harbour a super-massive black- hole in their cores – Existence of Intermediate Mass Black Holes uncertain Evidence for SMBHs • We find that stars have veloci es 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
v2r (110#103 )2 # 2.5#3#1016 M = = CORE G 6.67#10"11 37 6 MCORE =1.4#10 kg = 6.8#10 M!
• In our Milky Way galaxy – Velocities > 1000 km/s inside 0.01 pc! 6 • => 2 x 10 Msun SMBH Our Galactic Centre Infrared Studies
• Infrared (2 µm) penetrates through the dust • Can use to probe stellar popula ons and dynamics in GC • Find central cluster of young massive stars
– Teff ~ 20,000 K – Burst of star forma on 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 kinema cs GM v2R – And mass of central object v2 = ! M = R G Time lapse movie of Galactic Centre over past 12 years Orbital Motions
Proper Motions in Galactic Centre • Measured by speckle and (now) adap ve op cs – 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! Obs.Tech. • Measures veloci es of many stars near GN • From veloci es: mass – At 0.01 pc: v ~ 1000 km/s – At 0.04 pc: v ~ 500 km/s • Implica on: v2R ! constant " M (r < 0.5pc)! constant i.e., Keplerian Central Black Hole • Mass of central object v2R M = G
6 • Mass within 0.01 pc is ~3 x 10 Msun • Keplerian veloci es inside of 0.5 pc
7 • Mass within 10 pc is ~3 x 10 Msun 6 -3 • mass density is ~4 x 10 Msun pc
• So, does this necessarily mean a black hole? 12 -3 • If not, mass density is ~4 x 10 Msun pc – Cluster of neutron stars? Mass distribution mass
107
6 3 x 10 Msun Msun
106
4 x 1012 M pc-3 6 -3 sun 4 x 10 Msun pc
105
0.01 0.1 1.0 10.0
Radius (pc) 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 5 – Luminosity < 10 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 GM Rsun R = c2 Flare from black hole • x-ray flare from central loca on • Due to mass falling into the GC super-massive black hole
• Heats up and emits in X- rays before crossing ‘event- horizon’ Quasars & Seyferts
• 1943 Carl Seyfert publishes a list of odd galaxies: – Mostly spirals with point-like nuclei – Broad emission lines – Also high ionisa on states (O[VI]) – Doppler interpreta on 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 dis nct regions: – Broad lines from Broad Line Region – Narrow lines from Narrow Line Region
Galaxies – AS 3011 16 NGC5548 (Seyfert I) NGC3277 (Normal Spiral)
Galaxies – AS 3011 17 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
18 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, iden fied as redshi ed hydrogen -Eventually deduced a redshi of 0.16 (Schmidt, Nature, 1963) -Soon other Quasars were discovered with redhis s upto 2 -Current record holder around z=6.0
Galaxies – AS 3011 19 3C273
Op cal jet
Galaxies – AS 3011 20 Typical Quasar or QSO spectrum
Steep con nuum Broad lines No discernable host galaxy point-like. Observa ons -> Proper es Point-like = compact Distant = luminous Broad lines = high veloci es High excita on lines = energe c Variable = small (<1 lyr)
Galaxies – AS 3011 22 O en have associated jets visible in ra o due to rela vis c charged material zipping out along open field lines:
Synchrotron radia on
Jets o en extend 10-500kpc!
at 1 Gpc Galaxies – AS 3011 23 Emit over all wavelengths:, e.g.,Mk421
24 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 (Op cally violently variable) LINERS - Weak Seyferts (no broad lines)
25 Galaxies – AS 3011 26 Theories Two compe ng theories: - Nuclear starbursts - Super-massive black holes 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 me implies emission from region only ~ light-weeks across (~0.01 pc) • Hence must have very high density, because 1/2 – fast orbits within very small region: vorbit ~ (G M / r) • Only a black hole can pack this much ma er in so densely – the power is generated at a few Schwartzschild radii 2 RS = 2 G Mbh / c (≈ 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
28 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 orbi ng further out – fastest stuff is in an accre on disk around the black hole
broad line region narrow line region clouds at ~0.1-1 kpc
accre on torus
(not to scale!) see Seyfert 2 can also see polarized light from see Seyfert 1 near the nucleus if sca ered 29 AGN Unification Antonucci, 1993 Blazar Quasar
Seyfert 2 galaxy
Torus
Seyfert 1 galaxy
30 Jet !!! Correla on between SMBH mass and bulge velocity dispersion
31 Correla on between SMBH mass and Bulge Absolute magnitude AGN ac vity AGN ac vity much more common in the past. Consistent with bulge forma on preceeding disc forma on The Cosmic Star-forma on History
Constructed from measurements of Hα or UV fluxes at various redshi s CSFH v AGN Ac vity
AGN ac vity does not seem to trace SFH at high-z
1. Data uncertain 2. Redshi axis misleading
…..lets switch to me à CSFH v AGN ac vity v Time
.
.
. Pu ng it together ? U Dark Ma er Baryonic Ma er SMBHs
0yrs AGN ac vity AGN Rapid COLLAPSE/MERGERS merging 5Gyrs
BULGES
AGN no longer ac ve INFALL Slow merging
DISKS
P-BULGES ACCELERATING DECELERATING 13Gyrs SECULAR ??
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