Spiral Galaxies

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Spiral Galaxies
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Elliptical Galaxies
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Irregular Galaxies
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Classification of Galaxies
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Properties of Galaxies
Spirals Ellipticals Irregulars
Mass typical range (solar masses) 1011 109 - 1012 1011.5 106 - 1013 1010 108 - 1011
Size (pc) 104- 105.5 104- 106 103- 105
Color Blue arms, reddish bulge reddish bluish
Luminosity 108 - 1010 105 - 1011 107- 109
Stellar Populations Pops I II Pop II Pop I (Pop II)
Interstellar medium Yes Very little Still some
Rotation Yes (disk) no Not a lot
Fraction 30 20 50
Other galaxy types Peculiar, Interacting, Ring,
Starburst, Dwarf, Luminous Infrared, Active
Nuclei, Damped Lyman-alpha
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Stephans Quintet Colliding galaxies
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The Anntenae Galaxies a case study
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Galactic Train Wrecks
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Collisional Aftermath
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Ring Galaxies the splash
Head-on collisions can produce a ripple of star
formation that expands outwards.
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Galactic Superwinds
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The Magellanic Clouds
Southern Hemisphere only
Large Magellanic Cloud
Small Magellanic Cloud
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The Galactic Neighborhood
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The Local Group of Galaxies
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Members of the Local Group
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And outward
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Galaxy Clusters
Virgo
Notice the giant ellipticals at the centers of
many clusters. These are an example of galactic
cannibalism.
Coma
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Galactic Cannibals Central CD Ellipticals
At the heart of rich clusters, galaxies pass
through the center and are disrupted and
collected.
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Making a CD galaxy
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into the Universe
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Large Scale Structure
On the largest scales (100 million ly) the
Universe takes on a foamy appearance, with
great filaments and walls of galaxies and
clusters, surrounding great voids that are
relatively empty.
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Dark Matter - rotation curves
Rotation curves imply the mass-to-light ratios of
galaxies go up as we look on larger scales Sun?
M/L1, solar neighborhood ? M/L3, galaxy ?
M/L50
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Dark Matter cluster speeds
galaxy clusters ? M/L200-500 From average speed
of galaxies the cluster would fly apart From
X-ray gas held in several million degrees and
extensive
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What could the dark matter be?

1. Normal but dark matter (baryonic) rocks,
   white or brown dwarfs?

2) Black holes or neutron stars? Too much
metals would have been produced.
Anyway, there is a fundamental reason from the
Big Bang this cant be it
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Dark Matter gravitational lensing
The mass required to produce the observed lensing
is much higher than the luminous mass. This is a
direct observation of gravity due to dark matter.
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WIMPS and Cold Dark Matter
Could dark matter be some kind of new particles
which interact very weakly with matter (like
neutrinos do) but massive, and not moving
relativistically? Experiments at Berkeley and
elsewhere are looking for them (guaranteed Nobel
prize!).