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Black Holes and Quasars

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Black Holes and Quasars 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 Unificaon SMBH correlaons with host galaxy AGN AcAvity with Cosmic Time Implicaons For galaxy Formaon 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-rotang black hole this is simply when the KineAc Energy = Gravitaonal 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 iniAal 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 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 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 populaons and dynamics in GC • Find central cluster oF young massive stars – Teff ~ 20,000 K – Burst oF star Formaon 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 kinemacs 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) 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! Obs.Tech. • 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 • Implicaon: 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 velocies 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 locaon • 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 ionisaon states (O[VI]) – Doppler interpretaon 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 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, idenAfied as redshied hydrogen -Eventually deduced a redshit oF 0.16 (Schmidt, Nature, 1963) -Soon other Quasars were discovered with redhiss upto 2 -Current record holder around z=6.0 Galaxies – AS 3011 19 3C273 OpAcal jet Galaxies – AS 3011 20 Typical Quasar or QSO spectrum Steep conAnuum Broad lines No discernable host galaxy point-like. Observaons -> ProperAes Point-like = compact Distant = luminous Broad lines = high velociAes High excitaon lines = energeAc Variable = small (<1 lyr) Galaxies – AS 3011 22 Oten have associated jets visible in rao due to relavisAc charged material zipping out along open field lines: Synchrotron radiaon Jets oten 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 (OpAcally violently variable) LINERS - Weak SeyFerts (no broad lines) 25 Galaxies – AS 3011 26 Theories Two compeAng 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 Ame 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 maer 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 orbiAng Further out – Fastest stuff is in an accreAon disk around the black hole broad line region narrow line region clouds at ~0.1-1 kpc accreAon torus (not to scale!) see SeyFert 2 can also see polarized light From see SeyFert 1 near the nucleus iF scaered 29 AGN Unification Antonucci, 1993 Blazar Quasar Seyfert 2 galaxy Torus Seyfert 1 galaxy 30 Jet !!! Correlaon between SMBH mass and bulge velocity dispersion 31 Correlaon between SMBH mass and Bulge Absolute magnitude AGN ac+vity AGN acAvity much more common in the past. Consistent with bulge Formaon preceeding disc Formaon The Cosmic Star-Formaon 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 . Pung it together ? U Dark Maer Baryonic Maer SMBHs 0yrs AGN acAvity AGN Rapid COLLAPSE/MERGERS merging 5Gyrs BULGES AGN no longer acAve INFALL Slow merging DISKS P-BULGES ACCELERATING DECELERATING 13Gyrs SECULAR ?? 37 .
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