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

•  Fath (1907) •  Slipher (1917) •  Hubble (1926 •  Seyfert (1943) •  Khatchikyan e Weedman (1971)

NGC 1068

•  1907 - Fath observou, no espectro de NGC 1068, 6 linhas em emissão, típicas de nebulosas planetárias.

•  1917 –Slipher obteve espectros melhores. •  1926 – Hubble obteve espectros de NGC 1068, NGC 4051 e NGC 4151. •  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:

•  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)