Active Galactic Nuclei Ay 16 April 8 2008

Active Galactic Nuclei Ay 16, April 8, 2008

AGN DEFINITION PROPERTIES GRAVITATIONAL LENSES BLACK HOLES MODELS

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)

Early History Carl Seyfert & strange emission line galaxies (1943) Birth of Radio Astronomy & discovery of strong sources = radio galaxies (40 -50’s) Greenstein & Schmidt & QSO’s (1963) Surveys of Extremely Blue Objects (60 -70’s) Surveys at other Wavelengths (70’s > )

SY 1 AGN Spectra SY 2 QSO

Mean UV QSO Spectrum

LBQSO Spectrum

NGC 4151 Typical SY 1

Seyfert 1 galaxy and quasar spectra are dominated by broad line regions, lines often showing doppler velocities of 0. 1 c 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

M 87 Core In X-rays

Markarian 231

Markarian 421 BL Lac in an E Galaxy Te. V Source

BL LAC • SED’s

Radio Galaxies M 87 = Virgo A

M 87 in the Radio (VLA)

M 87 Central Jet

M 87 Jet In 3 bands

Centaurus A Radio on Optical Image

Cygnus A (VLA Conway & Blanco)

Synchrotron Power = related to kinetic enegy of electron = (1 - (v/c)2)-1/2 = (1 - 2)-1/2 where = v/c

Synchrotron Spectra

AGN NORMAL LINERS Baldwin, Phillips & Terlevich

Ly Alpha Forest

Eddington Luminosity Largest Luminosity that can pass through a gas in hydrostatic equilibrium : Outward Force of Radiation Pressure > Inward Force of Gravity d. P/dr = - g = -GM /r 2 Luminosity d. P/dr = -( T /mpc) (L/4 r 2) T = Thomson Cross section LEdd = 4 GMmpc/ T = 3. 3 x 104 L (M/M )

Gravitational Lensing Deflection of Light passing at a distance b by an object of mass M: = 4 GM/bc 2 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”

Gravitational lensing:

2237+0305 = Einstein’s Cross

Gravitational Redshift Photons lose E as the move out of a gravity well. For a photon E = hc/ , “m” = E/c 2 = h/c Gravitational Potential E = -GMm/r E = -GMh/c r / = GM/rc 2 which generally is pretty small except for NS and BH

Black Holes Curvature around a point mass has a critical radius = Schwarzchild Radius Inside this is a singularity RS = 2 GM/c 2 In units we know RS = 3. 0 km (M/M ) Gravitational redshift from RS =

NGC 4261 X-ray vs Optical

V = 1100 km/s

M 87’s central mass: Given the HST observations, what’s the enclosed mass? v = 1100 km/s ~ 1” D = 16. 1 Mpc R = 0. 078 kpc (78 pc) GMm/R = 1/2 m. V 2 for circular orbits M = 0. 5 V 2 R/G G = 4. 309 x 10 -6 kpc (km/s)2 / M Mcore ~ 1010 M

Reverberation Mapping NGC 5548

Lag ~ 20 days Size ~ 20 light days ~ 0. 02 pc

Maggorian Relation (Nuker team) Almost every large galaxy has a central BH, and the BH mass is directly correlated with the galaxy’s total bulge mass!

A Unified Model of AGN’s 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.

Unified AGN Model BH + Disk + Torus SY 2 SY 1 BL Lac edge on tilted down the pipe