Unlike stars, galaxies aren’t born every day.
So we need to look back in time. The Hubble Deep Field.
A timeline.
We assume H and He was fairly uniform in the beginning universe BUT
It had small variations in density
Protogalactic clouds condense until first stars form.
Then galaxies form their halo (population II stars)
Spirals get disk collapse
Smaller clouds come together for bigger spirals
Why the difference between spirals and ellipticals?
Angular momentum?
Density?
But we can also form ellipticals by collision. 1 2 model
The biggest are the galactic cannibals called Central Dominant Galaxies 1 2
Or hot gas in galaxy clusters can strip the gas from a galaxy.
Collisions (or even tidal interaction) can trigger a starburst galaxy.
Sometimes these are shrouded in dust but it shows up in IR
What is this? the red shows radio waves.
Quasars and other
AGNs
The brightest of the AGN are quasars.
Nearby fainter ones are called Seyfert galaxies.
Quasars –strong emission lines, very redshifted,
some are
radio-loud
The power source - a supermassive black
hole with accretion
Sometimes you get jets model computer model Cyg A model
A variety of radio galaxies 1 2 3 4
Why do you need a black hole? It is 100 more efficient than fusion.
Do we have it right? Weighing
supermassive black holes
The newest look.
Light from quasars shows us the protogalactic clouds
