Historical overview

AGN
1.1 Historical overview
(Netzer chapter 1)
1.1.1 – The discovery of quasars
•  Radio astronomy
•  Lunar occultations
•  The redshift interpretation
Radio telescopes -­‐ Karl Jansky discovered, in 1931, tdescobriu ondas radio emission from the Milky Way -­‐Modern antenas: Parkes (Au) The precise location of radio sources: lunar occultations
3C 273 – the first Quasar (quasi-stellar objct) discoveredin 1963
Object 273 from the third Cambridge Catalog of radio sources
The spectrum of the first quasar: 3C 273
redshift z = Δλ/λ = v/c = 0.158
distance of 2.4 billion light-years
luminosity = 1000 galaxies
Maarten Schmidt (1929-)
in 1963
3C 279 - The variability and time-scale
l ~ ct (a few light-months)
1.1.2 –The Seyfert galaxies
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Fath (1907)
Slipher (1917)
Hubble (1926
Seyfert (1943)
Khatchikyan e Weedman (1971)
NGC 1068
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1907 - Fath observou, no espectro de NGC 1068, 6 linhas em emissão,
típicas de nebulosas planetárias.
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1917 –Slipher obteve espectros melhores.
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1926 – Hubble obteve espectros de NGC 1068, NGC 4051 e NGC 4151.
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1943 – Carl Seyfert identificou 6 galáxias com núcleos semelhantes,
acrescentando NGC 1275, NGC 3516 e NGC 7469.
NGC 3516
NGC 4051
NGC 7469
The 6 “Seyfert galaxies” (1943)
NGC 4151
NGC 1068
NGC 1275
Khatchikyan and Weedman (1971): Seyfert 1 e 2
1.1.3 – Identification of the first radio-galaxy
•  Baade e Minkowski (1954): Cyg A
In 1954, W. Baade e R. Minkowski
identified a radio-source
with a weak galaxy at z=0.057
(Cyg A)
3C175
z=0.77 V=16.6
Cygnus A (3C405)
z=0.056 V=17.0
The radio-galaxy
Centaurus A
M 87
1.1.4 – LINERS
(Low Ionization Nuclear Emitting Regions)
•  Heckman (1980)
1.1 5 – The continuum emission
•  Quasares with strong radio emission(radio-loud): 10%
Quasares with weak radio emission (radio-quiet): 90%
Quasares emission in all spectral ranges
The average spectrum from more than 700 quasars
1.1.6 - Variability
•  NGC 5548
Variability of NGC 4151
in the optical and X-Rays
1.1.7 – The AGNs zoo
AGN:
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QSO
Quasar
Radio-galaxy
NLRG
•  NLXG
•  Blazar (BL Lac object)
•  OVV
•  Seyfert Galaxy (type 1 and type 2)
•  LINER
How to find AGNs
•  Radio (3C;PKS (Parkes); NVSS (NRAO VLA); FIRST).
•  Optical – UV (Byurakan; Tololo; LBQS; Palomar QUEST;
Palomar Green; 2DF; SDSS; GALEX).
•  Infrared (IRAS; 2MASS; WISE)
•  X-Rays (ROSAT; Chandra; XMM-Newton; Swift)