Revealing images produced by one of the world’s most sophisticated
telescopes are enabling a team of Edinburgh astronomers to see clearly
for the first time how distant galaxies were formed 12 billion years
ago. Scientists from the UK Astronomy Technology Centre (UK ATC) and the
University of Edinburgh have been targeting the biggest and most distant
galaxies in the Universe with the world’s most sensitive submillimetre
camera, SCUBA. The camera, built in Edinburgh, is operated on the James
Clerk Maxwell Telescope in Hawaii. The images, published in Nature
tomorrow (18 September), reveal prodigious amounts of dust-enshrouded
star formation which could ultimately tell scientists more about the
formation of our own galaxy.

It is thought these distant galaxies in the early Universe will evolve
into the most massive elliptical galaxies seen at the present day. These
giant galaxies consist of 1000 billion stars like our Sun and are found
in large groups or clusters.

Dr Jason Stevens, astronomer at the UK ATC in Edinburgh explained why
understanding the evolution of these galaxies is so important. “The
distant, youthful Universe was a very different place to the one we
inhabit today. Billions of years ago, massive galaxies are thought to
have formed in spectacular bursts of star formation. These massive
elliptical galaxies have relatively simple properties. We hope that by
understanding how simple galaxies form we will be one step closer to
understanding how our own, spiral, Milky Way galaxy formed”.

Prof. Jim Dunlop, Head of the University of Edinburgh’s Institute for
Astronomy said: “For a long time astronomers have anticipated that the
formation of the most massive galaxies should have been a spectacular
event, but failed to find any observational evidence of massive galaxy
formation from optical images. Now we have discovered that it is indeed
spectacular, but because of the effects of interstellar dust, the
spectacle is only revealed at submillimetre wavelengths.” The dust
absorbs the bright blue light emitted by young stars. The energy from
the light heats the dust and makes it glow. It is this glow that is
detected by the SCUBA camera.

Dr Stevens and his colleagues suspected that these massive galaxies
would form in particularly dense regions of space so they chose regions
of very distant space that are known to be very dense because they
contain massive radio galaxies – galaxies which emit high levels of
radio waves. They found that many of the radio galaxies have near-by
companion objects that had not previously been detected at any
wavelength. Dr Rob Ivison, also at the UK ATC, described what they
found. “The companion objects are located in the densest parts of the
intergalactic medium, strung out like beads of water on a spider’s web
due to the filamentary structure of the Universe”.

The SCUBA images support a popular current model of galaxy formation in
which today’s massive elliptical galaxies were assembled in the early
Universe in dense regions of space through the rapid merging of smaller
building blocks.

IMAGES

1. The SCUBA images. These images show massive galaxies caught in the
throes of formation. The stars are forming so rapidly that an entire
galaxy can be built in a short timescale (cosmologically speaking, so a
billion years or so). The star formation in these galaxies is thought to
be driven by mergers of older galaxies in a filamentary structure
spanning millions of light years. In billions of years time, this
structure is predicted to become a cluster of giant elliptical galaxies
similar to those we see today in the local Universe.

The images were taken with the SCUBA camera at the James Clerk Maxwell
Telescope at a wavelength of 0.85 mm. The radiation detected comes from
a massive amount of small grains of cosmic dust made of carbon and
silicate that glow because they are heated by blue light from hot young
stars. Each image is centred on a distant Radio Galaxy. A radio galaxy
is so called because it emits jets of high speed plasma that originate
close to a massive black hole at its centre, and emit strongly at radio
wavelengths – the tick marks in the image show the direction of these
jets.

From left to right and top to bottom the images are centred on the
following radio galaxies: 4C41.17, 4C60.07, 8C1435+635, 8C1909+722,
B3J2330+3927 and PKS1138-262.

2. Abell 2218. This is an optical image taken with the Hubble Space
Telescope which shows a cluster of massive elliptical galaxies. This
cluster illustrates what the forming galaxies will eventually look like.
Photo credit: NASA

3. The James Clerk Maxwell Telescope.
Photo credit: Royal Observatory, Edinburgh

4. Summit of Mauna Kea, a 14000ft dormant volcano on the Big Island,
Hawaii. The James Clerk Maxwell Telescope can be seen down in the valley
in the centre of the picture.

Photo credit: Image courtesy of the James Clerk Maxwell Telescope, Mauna
Kea Observatory, Hawaii

NOTES FOR EDITORS

How do astronomers look back in time?

The further light has to travel across the universe before it reaches
the earth, the longer it takes to get here. That may sound obvious but
it is very useful for astronomers. It means that when they look at
objects in the furthest reaches of the universe, the light which is
captured by the telescope and camera has taken most of the age of the
universe to reach the earth. In other words they are also looking back
in time to how the universe was shortly after it formed.

However, it is not as easy as it sounds. On its way across the universe
the light becomes stretched (because the universe is expanding) so that
when it reaches the earth it is at much longer wavelengths than it was
when it was originally emitted. This is known as ‘red-shift’.

The light from the star-forming galaxies in this study has been
stretched so much that it has been shifted from the far-infrared
waveband, accessible only from space, to the submillimetre waveband.
Submillimetre radiation is emitted in the region of the electromagnetic
spectrum which lies between infrared light and radio waves. Because it
is absorbed by water vapour in the atmosphere it can only be detected
from the Earth’s highest mountains – in this case the 14,000ft Mauna Kea
on Hawaii. The radiation that we detect is predominantly produced by a
population of young hot young stars. This star-light is absorbed by
small grains of graphite and silicate – ‘interstellar dust’ – and is
re-radiated at longer far-infrared and submillimetre wavelengths.

The James Clerk Maxwell Telescope (JCMT)

The JCMT is the world’s largest single-dish submillimetre telescope. It
collects faint submillimetre signals with its 15 metre diameter dish. It
is situated near the summit of Mauna Kea on the Big Island of Hawaii, at
an altitude of approximately 4000 metres (14000 feet) above sea level.
It is operated by the Joint Astronomy Centre, on behalf of the UK
Particle Physics and Astronomy Research Council, the Canadian National
Research Council, and the Netherlands Organisation for Scientific
Research.

SCUBA

SCUBA (the Submillimetre Common-User Bolometer Array) is the world’s
most powerful submillimetre camera. It is attached to the James Clerk
Maxwell Telescope, and contains sensitive detectors called bolometers,
which are cooled to 60 milliKelvin, 0.06 degrees above absolute zero (60
milliKelvin is about -273.1 Celsius, -459.6 Fahrenheit). SCUBA was built
in the UK by the Royal Observatory, Edinburgh, at what is now the UK
Astronomy Technology Centre.

The UK ATC

The UK Astronomy Technology Centre is located at the Royal Observatory,
Edinburgh (ROE). It is a scientific site belonging to the Particle
Physics and Astronomy Research Council (PPARC). The mission of the UK
ATC is to support the mission and strategic aims of PPARC and to help
keep the UK at the forefront of world astronomy by providing a UK focus
for the design, production and promotion of state of the art
astronomical technology.

The ROE

The Royal Observatory, Edinburgh comprises the UK Astronomy Technology
Centre (UK ATC) of the Particle Physics and Astronomy Research Council
(PPARC), the Institute for Astronomy (IfA) of the University of
Edinburgh and the ROE Visitor Centre.

PPARC

The Particle Physics and Astronomy Research Council (PPARC) is the UK’s
strategic science investment agency. It funds research, education and
public understanding in four broad areas of science – particle physics,
astronomy, cosmology and space science.

PPARC is government funded and provides research grants and studentships
to scientists in British universities, gives researchers access to
world-class facilities and funds the UK membership of international
bodies such as the European Organisation for Nuclear Research, CERN, the
European Southern Observatory and the European Space Agency. It also
contributes money for the UK telescopes overseas on La Palma, Hawaii,
Australia and in Chile, the UK Astronomy Technology Centre at the Royal
Observatory, Edinburgh and the MERLIN/VLBI National Facility.

CONTACTS

  • Eleanor Gilchrist 0131 668 8397 PR Officer, ROE efg@roe.ac.uk

  • Dr Jason Stevens 0131 668 8441 Astronomer, UK ATC jas@roe.ac.uk

  • Dr Rob Ivison 07764 145817 Astronomer, UK ATC rji@roe.ac.uk

  • Professor Jim Dunlop 0131 668 8349 Head of the Institute for Astronomy jsd@roe.ac.uk

  • Julia Maddock 01793 442094 Press Officer, PPARC julia.maddock@pparc.ac.uk

  • Ronald Kerr 0131 650 9547 Press Officer, University of Edinburgh Ronald.Kerr@ed.ac.uk

  • Douglas Pierce-Price +1 808 969 6524 Outreach Officer, Joint Astronomy Centre d.pierce-price@jach.hawaii.edu

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