Structure 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 itself … The search for and origin of planetary systems … Origin and evolution of structure in the Universe

Some Fundamental Questions? understand the mechanics of the main structures found in the UniverseLast 20 years: understand the mechanics of the main structures found in the Universe. understand the origin and formation of these structureNext 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?

Image the “cosmic microwave background radiation” (CMBR) years after the Big Bang CMBR was in equilibrium with matter. Structure at this epoch locked into structure of the CMBR ,000 years 14,000,000,000 years Time Now Big Bang Microwave background radiation CAT image The Experiment: To image the seeds of the structure Requirement: Very sensitive detection at radio frequencies

The Developments: To image the seeds of the structure Specialist telescopes are required which are very sensitive for frequencies GHz : Small experiments including “The Very Small Array”  first conclusive results on the structure  agreement between experiments : 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? Requirements: Observe all the components of a galaxy gas in various 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 : 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: High resolution telescopes to probe 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 ? The HST mirror is 2.5m diameter  interferometer size of 100’s m  100’s times the resolution of HST. 50 mas 10 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 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 : X-ray observatories available (AXAF, XMM)  probe hot gas around groups of galaxies : Computing power sufficient to perform “experiments”

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 Searching for exotic particles Probe new phenomena

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