Structure Formation in the Universe

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Structure Formation in the Universe
Central problems in astrophysics The structure
of the Universe itself The search for and
origin of planetary systems Origin and
evolution of structure in the Universe

• Concentrate on the origin of structure in the
  Universe
• How do we make progress?
• What are the key problems for the next 20 years?
• What would we most like to know?
• How can we obtain this information?

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Some Fundamental Questions?

• Last 20 years understand the mechanics of the
  main structures found in the Universe.
• Next 20 years understand the origin and
  formation of these structure.

• What are the seeds of structure?
• How do stars form and how is their formation
  regulated?
• What effects do Active Nuclei have in the
  evolution of galaxies?
• When do the first galaxies appear?

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The Experiment To image the seeds of the
structure

• Image the cosmic microwave background radiation
  (CMBR).
• 300 000 years after the Big Bang CMBR was in
  equilibrium with matter.
• Structure at this epoch locked into structure of
  the CMBR.

CAT image
Requirement Very sensitive detection at radio
frequencies
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The Developments To image the seeds of the
structure

• 1999-2005 Small experiments including The Very
  Small Array ? first conclusive results on the
  structure ? agreement between experiments
• 2005-2010 Space born missions to improve
  sensitivity Planck Surveyor. ? Observations
  of CMBR produce definite answers ? Important
  results also for basic theories of the Universe

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The Experiment What controls the formation of
stars?
Galaxies form stars at very different rates ?
availability of raw material (gas)? ? galactic
collisions? ? self regulation?
Galaxies are complicated physical systems with
not only stars, but also gas in various states,
dust and radiation ? the InterStellar
Medium (ISM).
Requirements Observe all the components of a
galaxy gas in various forms, dust etc
An interacting galaxy
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The Developments A millimeter array

• 2005-2015 The MMA will operate on a site
  probably in Chille ? 40 dishes connected as an
  interferometer. ? Observe emission from
  molecules and dust. ? Detailed view of how
  stars form and the ISM in galaxies.

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The Experiment AGN and galaxy evolution

• A small fraction of galaxies contain an Active
  Nucleus (AGN) ? probably a supermassive black
  hole ? gas falls towards BH (accretion) ?
  energy
• AGN in some emits two jets of plasma ? interact
  strongly with their environment
• Immense power of AGN ? do the modify evolution
  of galaxy

Requirements High resolution telescopes to probe
the working of the AGN
HST optical image 0.8 microns
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The Developments Optical interferometers

• Worlds first optical interferometry COAST ?
  prototype for (most) future optical telescopes
  2000 - ?
• The HST mirror is 2.5m diameter ? interferometer
  size of 100s m ? 100s times the resolution of
  HST.

50 mas
10 days later
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The Experiment To find the first galaxies

• Understand basic properties of star
  formation/galaxies ? guess how a young galaxy,
  or protogalaxy would appear
• Consider also HST deep field observations.

• New stars very blue will appear redder at large
  distances (redshift).
• Dust protects gas from radiation. Dust is heated
  and is luminous at infrared wavelengths.
• Main raw material is hydrogen.
• Gas in close to a group of galaxies (cluster) may
  become very hot and emit X-rays.

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The Developments Infrared and Radio Telescopes

• 2000 Have a good idea what to loo for. Also
• 2010? Space-born telescope to work at far
  infrared (SIRTF) ? observe the dust emission
  from very young galaxies.
• 2005 Indian radio telescope GMRT ? may have
  sensitivity to observe the neutral hydrogen.
• 2000-2010 X-ray observatories available (AXAF,
  XMM) ? probe hot gas around groups of galaxies
• 2000-2020 Computing power sufficient to perform
  experiments

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And beyond 20 years

• To date, and probably next 20 years, our view of
  the Universe has come mainly from
  Electromagnetic Radiation
• Experiments will mature to extend our view of the
  Universe Gravitational Waves Neutrinos Searc
  hing for exotic particles
• Probe new phenomena

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Conclusions

• The origin of the structure in the Universe is
  one of the most fundamental problems in
  astrophysics.
• This is likely to be a field where significant
  progress is make in the next 25 years as new
  telescopes now in the planning stages will prove
  powerful tools ? Observe stars in process of
  formation ? Learn about control of the formation
  of stars and ISM ? Discover seeds of structure
  we now observe ? Observe raw materials of
  structure at early epochs ? Observer first
  Galaxies