steward observatory – gregory rudnicksept 2006 recipe for a galaxy cluster: a lot of dark matter,...
TRANSCRIPT
Steward Observatory – Gregory Rudnick
Sept 2006
RECIPE FOR A GALAXY CLUSTER: A LOT OF DARK
MATTER, A BUNCH OF HOT GAS, AND A SPRINKLING OF
GALAXIES
Dr. Gregory Rudnick(NOAO/Kitt Peak)
Steward Observatory – Gregory Rudnick
Sept 2006
Some BIG questions about galaxy clusters?
What are they? How do they form? Where do they live? Why are they interesting? What are some current efforts to study them?
Steward Observatory – Gregory Rudnick
Sept 2006
A review of gravity
Gravity is a force
Everything attracts everything else
Without gravity everything would move in straight lines
Steward Observatory – Gregory Rudnick
Sept 2006
What are galaxy clusters?Large groups of galaxies held together by gravity.
6 Million light years
Steward Observatory – Gregory Rudnick
Sept 2006
What are galaxy clusters?
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Ben Moore
Large groups of galaxies held together by gravity.
Steward Observatory – Gregory Rudnick
Sept 2006
What are clusters made of?
galaxies
Hercules cluster
Steward Observatory – Gregory Rudnick
Sept 2006
An Interlude: Galaxies 101 (in 3 minutes)
There are hundreds of billions of stars in every galaxy
That’s about 200,000,000,000 stars!!
Galaxies are large collections of stars with gas and dust
Steward Observatory – Gregory Rudnick
Sept 2006
Hundreds of galaxies
That’s trillions of stars!!
Elliptical and S0 galaxies are the most common types of galaxies
Steward Observatory – Gregory Rudnick
Sept 2006
How massive are clusters?
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Use motions of galaxies.
Calculate how much mass you need to hold cluster together.
clusters are 1015 times as massive as the sun
Stars make up only 5% of cluster mass!
Where is the missing mass?
Steward Observatory – Gregory Rudnick
Sept 2006
Stars aren’t the only game in town
Matter emits at other wavelengths too.
Hot (10 million degree) gas emits in the x-ray
Twice as much hot intra-cluster gas as stars
Hot gas makes up 10% of total mass
Steward Observatory – Gregory Rudnick
Sept 2006
Where is the rest of the mass?
Only 5% stars + 10% hot gas has been seen
Where is other 85%?
Can we verify the large mass?
Gravitational lensing
Galaxy clusters are mostly made of
“Dark Matter”
Steward Observatory – Gregory Rudnick
Sept 2006
What do we know
Clusters are made of: galaxies (5%) hot gas (10%) dark matter (85%)
Steward Observatory – Gregory Rudnick
Sept 2006
How do they form?
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volker springel
Steward Observatory – Gregory Rudnick
Sept 2006
Where do clusters live?The nearest two clusters
Coma (260 million light years)
Virgo (55 million light years)
Steward Observatory – Gregory Rudnick
Sept 2006
The Big Picture
Steward Observatory – Gregory Rudnick
Sept 2006
The Big Picture
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Steward Observatory – Gregory Rudnick
Sept 2006
Why are clusters interesting and useful?
Providing evidence for dark matter
Gravitational lensing
Steward Observatory – Gregory Rudnick
Sept 2006
Steward Observatory – Gregory Rudnick
Sept 2006
The Bullet Cluster - testing the existence of Dark Matter
Douglas Clowe
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If gravity is stronger on large scales and dark matter doesn’t exist then the gravitational force should be located at the center of the “visible” matter.
Steward Observatory – Gregory Rudnick
Sept 2006
The Bullet Cluster
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Douglas Clowe
Use gravitational lensing to measure total mass.
Steward Observatory – Gregory Rudnick
Sept 2006
Clusters as Laboratories of Galaxy Evolution
Can clusters tell us how galaxies might transform their types?
How can a spiral turn into an elliptical?
Steward Observatory – Gregory Rudnick
Sept 2006
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What happens to gas in a galaxy when it flies through the hot intra-cluster gas
Ram Pressure Stripping
Steward Observatory – Gregory Rudnick
Sept 2006
Galaxy Harassment
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Steward Observatory – Gregory Rudnick
Sept 2006
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Galaxy Harassment
Steward Observatory – Gregory Rudnick
Sept 2006
Observing the Evolution of Clusters
How can we see clusters when they were younger?
Astronomy is like archaeology.
increasing distance
back in time
Steward Observatory – Gregory Rudnick
Sept 2006
CL1202.4-1224
4.3 Billion years
CL1232.3-12505.1 Billion years
CL1037.5-1243
5.3 Billion years
CL1054.4-1245
6.3 Billion years
CL1354.1-1231
6.3 Billion years
Clusters through cosmic time
Steward Observatory – Gregory Rudnick
Sept 2006
Galaxies in Young Clusters
cl1037-1243 5.3 Billion years
cl1216-12016.5 Billion years
Steward Observatory – Gregory Rudnick
Sept 2006
Summary
Galaxies don’t matter: Clusters are dominated by Dark Matter (5% stars, 10% hot gas, 85% dark matter)
Cosmic meeting points: Clusters are concentrations of galaxies at the intersection of filaments of cosmic structure
Cosmic Laboratories: Clusters are useful in studying dark matter and the evolution of galaxies