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Active Galactic Nuclei

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Birth of Radio Astronomy & discovery of strong sources = radio galaxies (40-50's) ... Lag ~ 20 days Size ~ 20 light days ~ 0.02 pc. Maggorian Relation (Nuker team) ... – PowerPoint PPT presentation

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Title: Active Galactic Nuclei


1
Active Galactic Nuclei
  • Ay 16, April 8, 2008

2
AGN
  • DEFINITION
  • PROPERTIES
  • GRAVITATIONAL LENSES
  • BLACK HOLES
  • MODELS

3
WHAT IS AN AGN?
  • Objects that emit significant amounts of
    radiation from non-thermal sources
  • (i.e. not stars or dust or thermal gas).
  • In order of discovery
  • Seyfert Galaxies
  • Radio Galaxies
  • Quasars
  • BL Lac Objects
  • LINERS (Low Ionization Emission Regions)

4
Early History
  • Carl Seyfert strange emission line galaxies
    (1943)
  • Birth of Radio Astronomy discovery of strong
    sources radio galaxies (40-50s)
  • Greenstein Schmidt QSOs (1963)
  • Surveys of Extremely Blue Objects (60-70s)
  • Surveys at other Wavelengths (70s gt )

5
  • SY1
  • AGN
  • Spectra
  • SY2
  • QSO

6
Mean UV QSO Spectrum
7
LBQSO Spectrum
8

9
  • NGC 4151
  • Typical
  • SY1

10
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11
  • Seyfert 1 galaxy and quasar spectra are dominated
    by broad line regions, lines often showing
    doppler velocities of 0.1c
  • Seyfert 2 galaxies spectra are dominated by
    narrower lines, 1-2000 km/s wide
  • LINER spectra are dominated by stars plus
    emission lines from multiple ionization states
    indicative of non-thermal excitation
  • BL Lac spectra show almost no features but strong
    continua

12

M87 Core In X-rays

13

14
Markarian 231
15
Markarian 421
  • BL Lac in an E Galaxy
  • TeV ? Source

16
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17

BL LAC SEDs

18
Radio Galaxies

M87 Virgo A
19
  • M87 in the Radio
  • (VLA)

20
  • M87
  • Central
  • Jet

21
  • M87
  • Jet
  • In 3 bands

22
  • Centaurus
  • A
  • Radio on
  • Optical
  • Image

23
  • Cygnus A (VLA Conway Blanco)

24
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25
Synchrotron Power
  • related to kinetic enegy of electron
  • (1 - (v/c)2)-1/2 (1 - ?2)-1/2
  • where ? v/c

26
Synchrotron Spectra
27
AGN
NORMAL
LINERS
Baldwin, Phillips Terlevich
28
Ly Alpha Forest
29
Eddington Luminosity
  • Largest Luminosity that can pass through a gas in
    hydrostatic equilibrium
  • Outward Force of Radiation Pressure
  • gt Inward Force of Gravity
  • Gravity dP/dr -?g -GM?/r2
  • Luminosity dP/dr -(?T?/mpc) (L/4?r2)
  • ?T Thomson Cross section
  • LEdd 4?GMmpc/?T
  • 3.3 x 104 L?(M/M?)

30
Gravitational Lensing
  • Deflection of Light passing at a distance b by an
    object of mass M
  • ? 4GM/bc2
  • Bending of light by the Sun
  • r 6.96 x 1010 cm M 1.989 x 1033 g
  • ? 8.47 x 10-6 radians 1.74

31
  • Gravitational lensing

32

22370305 Einsteins Cross
33
Gravitational Redshift
  • Photons lose E as the move out of a gravity well.
  • For a photon E hc/?, m E/c2 h/c?
  • Gravitational Potential E -GMm/r
  • ?E -GMh/c?r
  • ??/? GM/rc2
  • which generally is pretty small except for NS
    and BH

34
Black Holes
  • Curvature around a point mass has a critical
    radius Schwarzchild Radius
  • Inside this is a singularity
  • RS 2GM/c2
  • In units we know
  • RS 3.0 km (M/M?)
  • Gravitational redshift from RS ?

35
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36
NGC 4261 X-ray vs Optical
37
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38

?V 1100 km/s
39
M87s central mass
  • Given the HST observations, whats the enclosed
    mass?
  • ?v 1100 km/s ? 1 D 16.1 Mpc
  • R 0.078 kpc (78 pc)
  • GMm/R 1/2 mV2 for circular orbits
  • M 0.5 V2R/G
  • G 4.309 x 10-6 kpc (km/s)2 / M?
  • Mcore 1010 M?

40
Reverberation Mapping

NGC5548
41

Lag 20 days Size 20 light days 0.02 pc
42

Maggorian Relation (Nuker team)
Almost every large galaxy has a central BH, and
the BH mass is directly correlated with the
galaxys total bulge mass!
43
A Unified Model of AGNs
  • We have come to believe that all AGN are
    essentially driven by the same phenomena --- a
    central black hole surrounded by an accretion
    disk, hot clouds of gas and dust. The disk is
    hot, 105 K plus. The AGN is powered by accretion
    onto the BH.
  • And what you actually see is driven by the
    viewing angle.

44
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45
Unified AGN ModelBH Disk Torus
  • SY2 SY1 BL Lac
  • edge on tilted
    down the pipe
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