Download Properties of Galaxies

Spiral Galaxies
Elliptical Galaxies
Irregular Galaxies
Classification of Galaxies
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
Stephan’s Quintet –
Colliding galaxies
The “Anntenae” Galaxies – a case study
Galactic Train Wrecks
Collisional Aftermath
Ring Galaxies – the “splash”
Head-on collisions can produce a “ripple” of star formation that
expands outwards.
Galactic Superwinds
Southern Hemisphere only
The Magellanic
Clouds
The Galactic Neighborhood
The “Local
Group” of
Galaxies
Members of the Local Group
And outward…
Galaxy Clusters
Virgo
Notice the giant ellipticals at
the centers of many clusters.
These are an example of
“galactic cannibalism”.
Coma
Galactic Cannibals – Central CD Ellipticals
At the heart of rich clusters, galaxies
pass through the center and are
disrupted and collected.
Making a CD galaxy
into the Universe…
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.
Dark Matter - rotation curves
Rotation curves imply the mass-to-light ratios of galaxies go up as we
look on larger scales: Sun M/L=1,
solar neighborhood  M/L=3,
galaxy  M/L=50
Dark Matter – cluster speeds
galaxy clusters  M/L=200-500
From average speed of galaxies – the cluster would fly apart
From X-ray gas held in – several million degrees and extensive
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 can’t be it…
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.
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!).