Review of spiral, elliptical, irregular and lenticular galaxies
Unlike stars, galaxies aren’t born every day.
So we need to look back in time. The Hubble Deep Field.
Spiral Galaxies:
Protogalactic clouds condense until first stars form.
Then galaxies form their halo (population II stars)
Disk forms Step 1 Step 2 Step 3 Step 4
Smaller clouds come together for bigger spirals
Elliptical Galaxies can form in these situations:
The protogalaxy has little angular momentum
The protogalaxy has a high density
Interstellar gas can be stripped out if the galaxy flies through the center of a dense galaxy-cluster
Collisions (example
NGC 2207 and IC 2163 and
Antenna)
can make elliptical galaxies (computer simulation
model)
and momentarily irregular looking galaxies (example
NGC 6240)
The biggest ellipticals
are the galactic cannibals called Central
Dominant Galaxies
Abell 3827
Irregular galaxies:
The timeline shows many irregular galaxies early in Universe's history
Another test on the formation hypotheses
We can detect protogalactic clouds by their absorption of distant quasar light
Starburst galaxies = galaxies with very large star formation rates
Collisions can trigger a starburst
Cartwheel Galaxy and "intruder" galaxy
compare with waves in a pond
Even "close encounters" can trigger a starburst
Large Magellanic Cloud
locations of M81 and M82
M81 and M82
Example of tidal effect Earth tides
Winds
Clustered supernova explosions blow winds
reason is similar to that of very large
fountains
M82 visible light
M82 in X-rays
Sometimes these are shrouded in dust but can be seen in the IR
The underlying galaxy is almost always a spiral or irregular
exceptional case of elliptical galaxy NGC3928, in which the
central starburst resulted from
the absorption of a small spiral galaxy
ApJ
Starbursts can use up most or all of the gas in a galaxy,
This causes a lull in subsequent star formation as the
galaxy waits for its ISM to rebuild from stellar winds and SN
Many galaxies have had starburst episodes in their past
How would a galaxy that had a starburst 5 billion years ago
look today?
Variations on the theme: Quasars, Seyfert galaxies, radio galaxies
Quasars:
example, visible light, redshifted
Discovery of Quasars (Quasi-Stellar Radio Sources) in 1960's
Absorption lines that were redshifted
Calculated velocity, distance, luminosity
Luminosity was huge
Bright in broad range of wavelengths: spectrum
Active Galactic Nucleus (AGN)
AGN = extremely bright center of a galaxy, where see galaxy, too
Examples, NGC5548 vs normal galaxy NGC3277 ,
NGC 1068 = M77
Same spectra as quasars
Can have jets, example:
nucleus and jet of M87
Radio Galaxies and Jets
Core-Jet-Lobe structure
Examples:
Cygnus A,
3C 353
Cartoon
More examples:
Centaurus A
3C 219
3C 31
NGC 1265
Compare
Cygnus A
with
"Herbig Haro Objects" (jets from protostar)
protostellar
jets model
is similar to
radio galaxy model
Radio Galaxies have molecular cloud donuts:
Cartoon
Radio Galaxies are really AGN viewed from different angle
Where does the energy come from ? !!
Material flowing into huge black hole in center
Jets are material flowing along twisted magnetic field
Cartoon
Another cartoon of a supermassive black hole with accretion
Finding the black hole mass from Kepler's 3rd law applied to orbits in
accretion disk
M87 Example
Supplemental Material: 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 or 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
