1. GALAXIES!

2. M82, nearby active galaxy, at 3.2 Mpc ~ 10 million lyrs

3. Optical
Infrared
X-ray

5. NGC 4594
Optical

6. NGC 4594
8 mm

8. NGC 628
(M74)

9. The merging Antennae Galaxy (NGC4038/4039)

10. Cartoon of a galaxy Halo Bulge Disk Spiral arms and
Bars are found in the disks
Haloes contain
Globular Clusters

11. What a Globular Cluster looks like…
From HST.
A cluster of stars all born at the same time. An excellent `clock’, as most globular clusters are roughly as old as the Universe.

12. Our Own Galaxy (Milky Way)

13. Galaxies have at least four basic shapes (morphologies)
Spirals
Progression from Sa to Sb, Sc, Sd, Sm depends on how tight the spiral arms are wound and how big is the bulge

14. Spiral arms can also show a variety of shapes
flocculent
Grand design
Spiral arms are easy to `see’ because they contain young, luminous stars (OB stars)

15. Barred spirals
Same progression as regular spirals: SBa, SBb, etc.

16. Ellipticals: E0, E3, E6
Ellipticals range in mass from about 20 times to as small as 1/100,000 our own Milky Way

17. Irregulars

18. This is the Hubble Turning Fork

20. A few more differences
Ellipticals do not rotate; they have `roundish’ shapes
Spirals do rotate; hence they appear as flattened pancakes

21. Disk rotation different from that of rigid bodies

22. Hence the idea of Dark Matter

23. Appearance of a galaxy is also linked to the history of its stellar populations
Elliptical galaxy: very old stars (red), formed very early in the life of the Universe
Irregular galaxy: stars have been forming more or less at a constant pace for most of the life of the Universe; many young stars, often blue in appearance
Spiral galaxy: stars have been forming at a decreasing pace over the entire life of the Universe, many young stars, esp. in spiral arms

24. Finally: most galaxies host SuperMassive Black Holes
These SMBHs are many million times heavier than normal BHs.

25. The Milky Way hosts a MBH!
The region towards the center of the MW, as seen by the Chandra X-ray telescope;
Our own MBH is about 4 million solar masses

27. The mass of the central BH is proportional to the mass of the galaxy’s bulge
Bulge Mass
SMBH
Mass
A recent discovery

28. Quasars Stands for `Quasi Stellar Radio Source’
They only exist in the distant Universe, and are linked to the young galaxies;
Perhaps when galaxies were forming, a lot of material was available to fall into the central BH, accrete it, and produce fantastic levels of energy and radiation.

29. Some of the unanswered questions
How have galaxies evolved to the large diversity we observe today?
How are the different morphologies formed, and when did they form?
How are stellar populations linked to the different morphological components (bulge, disk, halo)?
What are these components telling us about the link between the dark matter and the baryonic (ordinary) matter?
How does the bulge knows about the central black hole?