Structure Formation in the UniverseStructure Formation in the Universe

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

Central problems in astrophysics… … The structure of the Universe itselfThe structure of the Universe itself… … The search for and origin of planetary systemsThe search for and origin of planetary systems… … Origin and evolution of structure in the UniverseOrigin and evolution of structure in the Universe

Some Fundamental Questions?Some Fundamental Questions?

• Last 20 years: understand the mechanics of the main structures understand the mechanics of the main structures found in the Universefound in the Universe.

• Next 20 years: understand the origin and formation of these understand the origin and formation of these structurestructure.

• 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?

• 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.

0 300,000 years 14,000,000,000 yearsTime

NowB

ig B

ang

Microwave background radiation

CAT image

The Experiment: To image the seeds of the structure

Requirement:Requirement:Very sensitive detection at radio frequenciesVery sensitive detection at radio frequencies

The Developments: To image the seeds of the structure

Specialist telescopes are required which are very sensitive for frequencies 30-800GHz.

• 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

The Experiment: What controls the formation of stars?

Galaxies form stars at very different rates: availability of raw material (gas)? galactic collisions? self regulation?

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Requirements:Requirements:Observe all the components Observe all the components of a galaxy gas in various of a galaxy gas in various forms, dust etc…forms, dust etc…

An interacting galaxy

Galaxies are complicated physical systems with not only stars, but also gas in various states, dust and radiation the InterStellar Medium (ISM).

The Developments: A millimeter array

Observe molecular and cold atomic gas which emit line radiation in the range 1 GHz to 800 GHz

• 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.

Interferometry, invented by Martin Ryle, is a very powerful and established technique in radio astronomy.

Mullard Radio Astronomy Observatory, South of Cambridge

HST optical image 0.8 microns

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:Requirements:High resolution telescopes to High resolution telescopes to probe the working of the AGNprobe the working of the AGN

The Developments: Optical interferometers

Higher resolution is achieved with large telescopes which are not effected by the Earth’s atmosphere

• World’s first optical “interferometry” COAST prototype for (most) future optical telescopes 2000 - ?

• The HST mirror is 2.5m diameter interferometer size of 100’s m 100’s times the resolution of HST.

50 mas10 days later

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.

The Developments: Infrared and Radio Telescopes

Need to observe at infrared wavelengths and also see neutral hydrogen at large redshifts.

• 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”

And beyond 20 yearsAnd 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 UniverseGravitational WavesNeutrinosSearching for exotic particles

• Probe new phenomena

ConclusionsConclusions

• 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