Understanding Active Galaxies: Characteristics, Emission, and Evolution

1. Active Galaxies • Definition – • Amount of Energy • Type of Energy • Non-thermal • Polarized • Other characteristics • Emission spectra • Hydrogen – Balmer series & Lyman alpha (121.6 nm), UV • N V (124.0 nm) • C IV (154.9 nm) • O VI (103.5 nm) • Forbidden emission lines

2. Synchrotron radiation F(n)=Fon-a a between 0.7 and 1.2 Active galaxy general characteristics - • L>1037 W (>10 billion L) • Non-thermal emission • Excessive amount of IR, UV, radio, x-ray • Small region of rapid variability • Bright nucleus • Explosive appearance/Jets • Broad emission lines

3. ULIRG • Very high redshift (z) • Very young/early galaxies • Lots of IR/dust • Lots of star formation • Earliest of all galaxies?

4. Seyferts • Characteristics • Bright nuclei, 100 billion L • Spiral like (90%) • 10% Normal spirals have Seyfert characteristics • Non-thermal, synchrotron continuum • Two different types • Type I • More common • Wide spectral features – high velocity • More luminous • UV, x-ray

5. Type 2 • Narrow emission lines • Strong in IR • Range of types, 1.5, 1.7, etc. Model? • Accretion disk (non-thermal) • High energy photons (x-ray, uv) • Black hole • Jets • Radio, or boosted to higher energies • Dust – IR source for type 2 • High/low velocity clouds

6. Type 1 Type 1.5 Type 2

7. Radio Galaxies • 1% of all galaxies • 10% of active • Level of emission is used to classify • Two groups • Compact • Extended • Jets – synchrotron, bipolar outflow • Lobes, 50-3000 kpc, electrons, protons

8. 3 types of extended radio galaxies • Classical double lobes • High luminosity • cD galaxies, ellipticals • Wide-angle tails, bent tails • Narrow tail sources • Low luminosity, high velocity galaxies • Compact sources have different energy profile (a ~ 0)

9. Cygnus A 100 kpc Radio, x-ray images

10. M87 3 billion M Black hole

11. M87 both X-ray radio

13. Quasars • Quasi-stellar objects (QSOs) • Characteristics • Star-like appearance • Broad emission lines • Absorption lines, especially if z>2 • Other absorption features • Broad features with velocities up to 0.2 c • Low velocity sharp lines – absorption/emission • Lyman – alpha forest – wide range of velocities

14. Most quasars visible light sources, or higher energy (x-ray, gamma-ray) • Non-thermal spectrum (a between 0, 1.6) • Variable – quick • High z values • Quasar evolution • Brightness varies with z (brighter at high z) • Very few at very high z • Peak at z~2.5 (1000x more/volume than today) • Peak of 1 QSO per 100 Mpc3

19. Unified Model • Look at model for Seyferts • Can be applied to all types of active galaxies • Must have a black hole! • Million – billions of M • Infall rates of 100 M /year needed • High luminosities – short lived

20. History? Step 1. First objects formed – what were they? ULIRG or Quasars or regular Galaxies? ULIRG Rare, hard to find QSOs – stand out, but not common at very high z Most distant object observed, z=10 (maybe) Step 1a. Formation of first galaxies, z=5-8? With massive black holes? First QSOs formed also (not all galaxies are QSOs) Step 2. Peak of QSO formation at z=2.5

21. Step 3. QSOs start to fade Not feeding them enough Step 4. QSOs become Seyferts? Or Radio? Less powerful, logical step Seyfert phase – relatively short Whole AGN phase – few billion years? Step 5. Normal, boring galaxies, with no major activity

22. Feeding the Monster Black hole powers AGNs Can you over feed a black hole? Yes! Radiation pressure limits infall Eddington Luminosity – LEdd = 3 x 104 (MBH/M) L

23. Most distant object? Abell 1835 IR1916 z=10! Much smaller than MW!

24. Most distant QSO SDSS J1148+5251 z=6.42

25. Gravitational Lensing

26. How many quasars? Lynx arc