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Here is an attempt at an overview of how the demo might appeal to the audiences, firstly the SWG and other astronomers, secondly the media, as below.
Popular science: Formation and evolution of galaxies
In the universe today, stars are formed when clouds of gas and dust collapse. A
typical galaxy like the Milky Way contains (check) 10^10 stars and ten times
that mass or gas and dust (or have I got that the wrong way round).
- The Milky
Way is a spiral galaxy. Others are bigger, smaller, elliptical, irregular - does
one sort evolve into another?
- Mergers and interactions - some galaxies form stars
steadily (like Milky Way - ?1Msun/yr), others have exhausted the raw materials
(usually ellipticals) and others (Starbursts) have orgies of star formation and
supernovae explosions.
- Some active galaxies contain more exotic processes -
collisions; matter plummeting into a central black hole; gigantic jets.
Optical telescopes show the stars in all their colours, or the average starlight from
distant galaxies, and indicate the age of stars. However some Starbursts are so
dusty they can only be seen in Infra-red, radio or X-ray emission. Jets of
rarified plasma from active galaxies also have characteristic signatures at
extremely long (radio) and short (X-ray) wavelengths. The violent processes
around black holes produces radiation at every wavelength but the exact
proportions give clues to the mass, environment and duration.
Have galaxies changed with time?
- The further away a galaxy, the more redshifted its
emission, and so multi-colour observations tell us the distance of a galaxy and
hence the time since its light left it.
- Ultra-sensitive observations let us look
back in time to when the universe was only a half or even a tenth of its age
today.
- Thus we can see if, when the universe was younger, there were more
starburst galaxies? More mergers - were galaxies closer together when the whole
universe was smaller? ... In addition, there may be unusual galaxies of unknown
type...
The GOODS data were taken by ... different ground-based
and satellite instruments run by
... countries. Converting the data to formats suitable
for comparison and lining everything up is a major
operation.
Data come in two forms: the images, and catalogues of
galaxies and their properties extraacted from images. But
galaxies look different at different wavelengths, and you
can miss a very faint object in, say, blue light but it
shows up in red or in radio. So you need to compare
images and catalogues and plot their properties rapidly.
(Size of data sets... summary of Demo processes...)
So will we find the most distant galaxies? Will we find
exotic objects? Starburst galaxies hidden in shrouds of
dust? Or will we 'just' get a clearer picture of how
different the universe was when it was younger...
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