Cosmologists 'See' The Cosmic Dawn
Scientists have used a computer
simulation to predict what the very early Universe would have appeared like 500
million years after the Big Bang. (Credit: Image courtesy of Durham
University)
ScienceDaily (Feb. 11, 2009) — The images, produced by scientists at Durham
University's Institute for Computational Cosmology,
show the "Cosmic Dawn" - the formation
of the first big galaxies in the Universe.
The Cosmic Dawn began as galaxies began
to form out of the debris of massive stars which died explosively shortly after
the beginning of the Universe. The Durham calculation predicts where these
galaxies appear and how they evolve to the present day, over 13 billion years
later.
The researchers hope their findings,
which highlight star forming galaxies, will improve their understanding of dark
matter – a mysterious substance believed to make up 80 per cent of the
mass in the Universe.
Gravity produced by dark matter is an
essential ingredient in galaxy formation and by studying its effects the
scientists eventually hope to learn more about what the substance is.
The research is published in the Monthly Notices of the Royal Astronomical
Society and was funded by the Science and Technology Facilities Council (STFC)
and the European Commission.
The work combined a massive simulation showing how structures grow in dark
matter with a model showing how normal matter, such as gas, behaves to predict
how galaxies grow.
Gas feels the pull of gravity from dark matter and is heated up before cooling
by releasing radiation and turning into stars.
The simulation images show which galaxies are forming stars most vigorously at a
given time. Although the galaxies are biggest at the present day, the rate at
which they are making new stars has dropped greatly compared with the rate in
the early Universe.
The calculations of the Durham team, supported by scientists at the Universidad
Catolica in Santiago, Chile, can be tested against new observations reaching
back to early stages in the history of the Universe almost one billion years
after the Big Bang.
Lead author, Alvaro Orsi, a research postgraduate in Durham University's
Institute for Computational Cosmology (ICC), said: "We are effectively looking
back in time and by doing so we hope to learn how galaxies like our own were
made and to understand more about dark matter.
"The presence of dark matter is the key to building galaxies – without dark
matter we wouldn't be here today."
Co-author Dr Carlton Baugh, a Royal Society Research Fellow, in the ICC, at
Durham University, said: "Our research predicts which galaxies are growing
through the formation of stars at different times in the history of the Universe
and how these relate to the dark matter.
"We give the computer what we think is the recipe for galaxy formation and we
see what is produced which is then tested against observations of real
galaxies."
Professor Keith Mason, Chief Executive of the Science and Technology Facilities
Council, said: "Computational cosmology plays an important part in our
understanding of the Universe. Not only do these simulations allow us to look
back in time to the early Universe but they complement the work and observations
of our astronomers."