1. ACTIVE GALAXIES and GALAXY EVOLUTION
Quasars,
Radio Galaxies,
Seyfert Galaxies and
BL Lacertae Objects
Immense powers emerging from ACTIVE GALACTIC NUCLEI:
it’s just a phase they’re going through!

2. First: Copernican Principle, Expanded
VERY IMPORTANT POINT: The expansion of the Universe shown by the Hubble Law should be independent of location in the Universe. EVERYONE WOULD SEE AN EQUIVALENT EXPANSION AWAY FROM THEM In other words, we do not believe we are at a “special” place in the universe.

3. How do we observe the life histories of galaxies?

4. Deep observations show us very distant galaxies as they were much earlier in time
(Old light from young galaxies)

7. How did galaxies form?

8. We still can’t directly observe the earliest galaxies

9. Our best models for galaxy formation assume:
Matter originally
filled all of space
almost uniformly
Gravity of denser
regions pulled in
surrounding
matter

10. Denser regions contracted, forming protogalactic clouds
H and He gases in these clouds formed the first stars

11. Supernova explosions from first stars kept much of the gas from forming stars
Leftover gas settled into spinning disk
Conservation of angular momentum

12. But why do some galaxies end up looking so different?
NGC 4414
M87
But why do some galaxies end up looking so different?

13. Why do galaxies differ?

14. Why don’t all galaxies have similar disks?

15. Conditions in Protogalactic Cloud?
Spin: Initial angular momentum of protogalactic cloud could determine size of resulting disk

16. Conditions in Protogalactic Cloud?
Density: Elliptical galaxies could come from dense protogalactic clouds that were able to cool and form stars before gas settled into a disk
Elliptical vs. Spiral Galaxy Formation

17. Start with the Mildly Active or Peculiar Galaxies
STARBURST galaxies 's of stars forming per year, but spread over some 100's of parsecs.
Other PECULIAR galaxies involve collisions or mergers between galaxies.
Sometimes produce strong spiral structure (e.g. M51, the "Whirlpool")
Sometimes leave long tidal tails (e.g. the "Antennae" galaxies)
Sometimes leave "ring" galaxy structures--an E passing through a S.
Sometimes see shells of stars around Es

18. Peculiar Galaxies: Starburst (NGC 7742) , Whirlpool (M51), Antennae (NGC 4038/9) in IR, Ring (AM )

19. Colliding Galaxies “Cartwheel” ring galaxy
Antennae, w/ starbursts and a simulation: a collision in progress
Collision Simulation Movie

20. Collisions may explain why elliptical galaxies tend to be found where galaxies are closer together
Stat here on 4/14

21. Giant elliptical galaxies at the centers of clusters seem to have consumed a number of smaller galaxies

22. Starburst galaxies are forming stars so quickly they would use up all their gas in less than a billion years

23. 4 MAIN CLASSES of AGN Radio Galaxies Quasars Seyfert Galaxies
BL Lacertae Objects (or Blazars with some Quasars and some Radio Galaxies)
All are characterized by central regions with NON-THERMAL radiation dominating over stellar (thermal) emission

24. Thermal vs. Non-Thermal Spectra. Normal mostly from stars,
Thermal vs. Non-Thermal Spectra Normal mostly from stars, Active mostly synchrotron

25. RADIO GALAXIES All are in Elliptical galaxies
Two oppositely directed JETS emerge from the galactic nucleus
They often feed HOT-SPOTS and and LOBES on either side of the galaxy
Radio source sizes often 300 kpc or more --- much bigger than their host galaxies.
Head-tail radio galaxies arise when jets are bent by the ram-pressure of gas as the host galaxy moves through it.
For powerful sources only one jet is seen: this is because of RELATIVISTIC DOPPER BOOSTING: the approaching jet appears MUCH brighter than an intrinsically equal receding jet since moving so FAST;
Can yield CORE DOMINATED RGs

26. Radio Galaxy: Centaurus A

27. Cygnus A and M87 Jet

28. Radio Lobes Dwarf Big Galaxy

29. Core Dominated RG (M86)

30. QUASAR PROPERTIES
QUASI-STELLAR-OBJECT: (QSO): i.e., it looks like a STAR BUT: NON-THERMAL SPECTRUM UV excess (not like a star)
BROAD EMISSION LINES  Rapid motions
VERY HIGH REDSHIFTS  not a star, but FAR away. The current (2008) convincing record redshift is z = 6.4, i.e., light emitted in FAR UV at 100 nm is received by us in the near IR at 740 nm!
HUGE DISTANCES  VERY LUMINOUS

31. NEWER QUASAR DISCOVERIES
Only about 10% are RADIO LOUD
Most show some VARIABILITY in POWER
OVV (Optically Violently Variable) QUASARS change brightness by 50% or more in a year and are highly polarized
QUASARS are AGN: surrounding galaxies detected, though small nucleus emits times MORE light than 1011 stars! “Brighter than a TRILLION suns”

32. Quasar 3C 273
Radio loud
Rare OPTICAL jet, but otherwise looks like a star
Relatively nearby quasar

33. Redshifted Spectrum of 3C 273

34. Typical Quasar Appearance
Most are actually very faint
BUT their huge redshifts imply they are billions of light-years away and intrinsically POWERFUL
Start here on 11/12