Announcements

1
Announcements

• Midterm III grades are online
• final projects due Monday April 30th
• review session for final Wednesday May 9th, 6pm

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Lecture 40Simulating the Universe in a computer
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Structure formation in the Big-Bang model
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Can astronomy help to discriminate between
neutrinos and neutralinos ?

• Neutrinos
• mass in the tens of eV ? very low mass
• very low mass ? high velocities ? hot
• can travel several tens of Mpc over the age of
  the universe
• Neutralinos
• mass in the hundredst of GeV ? very high mass
• very high mass ? low velocities ? cold
• cannot travel significant distances over the age
  of the universe

• Neutrinos Hot Dark Matter (HDM)
• mass in the tens of eV ? very low mass
• very low mass ? high velocities ? hot
• can travel several tens of Mpc over the age of
  the universe
• Neutralinos Cold Dark Matter (CDM)
• mass in the hundredst of GeV ? very high mass
• very high mass ? low velocities ? cold
• cannot travel significant distances over the age
  of the universe

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Can astronomy help to discriminate between hot
and cold dark matter ?
CDM
HDM
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Structure formation HDM vs CDM

• CDM fits observations much better than HDM
• high-z galaxies are smaller
• irregular shape of galaxy clusters indicate that
  they formed recently
• there are only a very few clusters at high
  redshift, but many galaxies
• two-point correlation function is much better
  reproduced

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Hierarchical structure formation
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A galaxy formation recipe

• Ingredients gas, radiation, gravity
• Pick a model for the Universe
• Add some seeds (perturbations) to trigger growth
  of structure
• Combine it with some recipe of your star
  formation cookbook

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65 Mpc
50 million particle N-body simulation
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65 Mpc
50 million particle N-body simulation
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65 Mpc
50 million particle N-body simulation
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65 Mpc
50 million particle N-body simulation
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65 Mpc
50 million particle N-body simulation
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A voyage through a CDM universe
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A voyage through a CDM universe
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Do ellipticals form by merging spirals ?
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Cartwheel galaxy
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Whirlpool Galaxy
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Back to spirals by smooth growth?
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Hierarchical galaxy formation
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Phase I Formation of First Galactic Disks (1Gyr)

• first relaxed small disks

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Phase II Bulge Formation and Disk Reassembly (2
Gyr)

• disks are destroyed by merging, formation of an
  elliptical
• later on disk reassemble

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Phase III Well Developed DiskBulge Structure (3
Gyr)

• slowly growing disk
• young stars and gas in thin disk, bulge of old
  stars

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Phase IV Tidally Triggered Bar Formation (5 Gyr)

• several minor mergers
• rapidly rotating bar

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Phase V Formation of a Giant Elliptical (7 Gyr)

• nuclear star burst consumes nearly all remaining
  gas

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Announcements

• Midterm III grades are online
• final projects due Monday April 30th
• review session for final Wednesday May 9th, 6pm