7 - 18 August 2000

Media release
>From Jacqueline Mitton (Meeting Press Officer)
phone: +44 (0)1223 564914

Phone contact 7 - 16 August [Meeting Press Room]
+44 (0)161 275 7832
+44 (0)161 275 9458
+44 (0)161 275 9499

Mobile phone 07770 386133

Date issued: 5 August 2000

NOT TO BE RELEASED BEFORE 8 p.m. BST, Wednesday 16th August 2000


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Dr Tom Shanks
Phone: +44 (0) 191 374 2171

Dr Nigel Metcalfe
Phone: +44 (0) 191 374 3806

Department of Physics,  University of Durham,
South Road, Durham DH1 3LE, UK.

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Summary:  So many bright galaxies are now being detected at very high
redshift (z>4), galaxies must be even older and have formed even earlier
than previously thought. 

Astronomers at Durham University (UK) have found new evidence that large
numbers of galaxies were in existence at even earlier times than previously
thought. They have identified many galaxies with redshifts between 4 and 6.
This means they were already in existence about 10 billion years ago, when
the universe was six times smaller than it is now. With this discovery,
researchers may have to rethink their ideas about how galaxies formed. The
work will be presented on Thursday 17th August by Dr Tom Shanks at a
symposium during the International Astronomical Union General Assembly in
Manchester (UK).

Because of the finite speed of light, pictures of very remote galaxies
(identifiable because their redshifts have high values) record them as they
appeared many billions of years ago, or even in the process of formation.
Observations of this kind directly test cosmological theories about how and
when galaxies formed. The most popular theories so far have said that
galaxies formed relatively recently and predict that hardly any galaxies
should be seen with high redshifts.

Now, new red and infra-red pictures have been taken of small areas of the
sky already targetted by the deepest ultraviolet and blue surveys. The new
images extend the search for galaxies to higher redshifts than every before.
Surprisingly, the new results show such large numbers of galaxies that there
seems to be almost as many bright galaxies with redshifts of 5 as there are
at low redshifts nearby! This makes the epoch of galaxy formation earlier in
the history of the universe than astronomers previously thought. 

Beyond The Final Frontier! 

The ground-based pictures come from the UK/Dutch 4.2-metre William
Herschel Telescope in the Canary Islands and from the 3.5-metre Calar Alto
Telescope in Spain. Tens of hours of exposure time went into a picture taken
in red light at the Herschel Telescope with another similarly long exposure
made in infrared light at Calar Alto. These pictures have been compared to
new pictures in infrared light taken with the Hubble Space Telescope in its
Hubble Deep Field North and to new optical and infrared pictures in the
Hubble Deep Field South. The Space Telescope exposure was a total of 120
hours in a single tiny patch of sky, observing in ultraviolet, blue and red
light. The Space Telescope pictures reach deeper (i.e. can see fainter
objects) than the ground-based pictures but they cover a smaller area of
sky. However, the basic result is that the counts of high redshift galaxies
from both the ground- and space-based experiments agree well, in the range
where they can be compared and so both these experiments appear to be giving
consistent results. 

In 1996, the ultraviolet and blue pictures in the Herschel and Hubble Deep
Fields revealed so many faint blue galaxies at a redshift of 2 that they
already challenged the claims of the most popular cosmological theory, which
suggested that galaxies formed around a redshift of 1, when the universe was
half as big as it is now. Since then, observations by Charles Steidel and
collaborators at the 10-metre Keck telescope confirmed the Durham group's
results by finding many galaxies at redshifts of 3 and 4. Now, applying
similar techniques as before but to the new red and infra-red pictures, Dr
Shanks and colleagues find large numbers of galaxies at the even higher
redshifts of 5 to 6. There are as many galaxies at these high redshifts as
are found locally. 

Dr Shanks says, "Four years ago, we described the galaxies we found at with
redshifts of 2 as being at 'The Final Frontier' because we thought that just
beyond them we might be looking back to a time before galaxies formed. Now
that large numbers of galaxies at even higher redshifts have been found, we
feel entitled to describe them as being Beyond the Final Frontier!". 


Deep Pictures as Time Machines.

Light travels at a speed of 300 000 kilometres per second. Although this
speed is high it is finite and this means that light takes about 8 minutes
to reach us from the Sun. The huge size of our Milky Way Galaxy means that
light takes about 25 000 years to reach us from the Centre of our Galaxy.
But the light from the faint galaxies seen in these deep pictures has come
from even farther away, so far away that the light has taken about 10
billion years to reach us!! This is close to the estimated age of the
Universe and hence the deep pictures are probing not only out in distance
but they probe back in time as well, since we can see galaxies as they
appeared early in the history of the Universe. In this sense the deep
pictures can be viewed as time machines allowing us to see deep into our
past. The allow cosmologists directly to observe galaxies in the process of
formation. Their theories can then be tested in detail. 

The ability to detect galaxies at redshifts as high as z=6 comes from the
new red and near-IR Hubble and Herschel deep pictures. Essentially they
allow much more accurate measurements of the colours of the faintest
galaxies, and the quality of these measurements is so high that the galaxy
colours become a very good substitute for galaxy spectra and this allows new
estimates of the galaxy redshifts to be obtained. 

Could we detect galaxies at even higher redshifts?

The detection of bright galaxies at z=4-6 opens up the question as to
whether galaxies at even higher redshift may exist. Though it would make
even more problems for theorists, the timespan between z=10 or z=20 and z=5
is incredibly short relative to the timespan between z=5 and z=0. To observe
galaxies at these redshifts we need even deeper pictures over a relatively
wide field, particularly at infra-red wavebands. The new Wide Field Camera
at the UK Infrared Telescope on Hawaii and the UK VISTA telescope in Chile
which will be available in a few years will open up these new redshift
regimes for observation. A few years later the giant NASA-ESA 6.5-metre Next
Generation Space Telescope (NGST) in which the UK has a share will be
launched to observe even deeper and further into the infrared with the prime
aim of detecting at the highest redshifts the dawn of the age of the

The Durham Cosmology Group.

The members of the Durham research team are Tom Shanks (Reader), Nigel
Metcalfe (Computer Officer), Dick Fong (Sen. Lecturer), and Geoff Busswell
(PhD student). The Durham Cosmology group has been active in the Deep
Imaging/ Galaxy Counts area since 1976. The group is very experienced in the
techniques of measuring the light from faint galaxies as the group has led
the way in faint galaxy research, first using machine measured photographs
to take detect galaxies at the B=20-24mag limits in the period (1976-1984).
They then used electronic CCD detectors on 4metre ground-based telescopes in
the period (1985-1996) and most recently using the Hubble Space Telescope
data , to probe from B=25mag to B=29mag. The group is also highly
experienced in the techniques of modelling the counts and colours of the
faint galaxies detected in these deep images. 

The Deep Pictures. 

Hard copies of the deep pictures, in colour, from the William Herschel
Telescope, the Calar Alto Telescope and the Hubble Space Telescope can be
obtained from Tom Shanks. 

This press release and the deep pictures, and instructions as to how to
obtain the paper, will be shown on the world-wide web site (after 8th
August) :