Scientists search for dark galaxies through the AGES (Forwarded)

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Scientists search for dark galaxies through the AGES

First results from the Arecibo Galaxy Environment Survey (AGES) suggest
the discovery of a new dark galaxy. The AGES survey, which started in
January 2006, is the most sensitive, large-scale survey of neutral
hydrogen to date. Neutral hydrogen is found in most galaxies and it is a
key tool in the search for dark galaxies as it can be detected even when
there are no stars or other radiation sources to "shine a light" on
matter.

The new candidate dark galaxy is located near NGC1156, an apparently
isolated, irregularly-shaped galaxy found at the edge of the Aries
constellation. The first observations in the AGES programme identified a
number of new galaxies. One newly discovered source is approximately 153
million light-years from Earth and appears to be 200,000 light-years
across. There is no obvious optical counterpart to the massive object.

Robbie Auld, who is presenting the results at the RAS National Astronomy
Meeting in Leicester on 6th April, said, "The new source showed up clearly
in the AGES survey as it contains huge amounts of hydrogen gas but it was
missed in all previous searches as it doesn't appear to contain many
bright stars. The interactions between hydrogen atoms in cosmic gas clouds
are enough to stimulate light emission at the neutral hydrogen
"fingerprint" wavelength of 21cm. In the first stage of the AGES campaign,
we have used the Arecibo radio telescope to search at this wavelength,
looking for galaxies that have remained hidden from astronomers in the
past. We now need to follow up observations at other wavelengths and work
out exactly how many stars this new galaxy may or may not contain."

The AGES programme, which will last for four years, is led by Cardiff
University's Dr Jonathan Davies. In addition to the Arecibo radio
telescope, AGES will use a network of ground-based and space-based
telescopes to observe the sky in many different wavelengths. Among those
used will be the UK Infrared Telescope in Hawaii, the GALEX ultraviolet
space telescope, the Hubble Space Telescope.

The techniques used in AGES have already been used on a small scale and
have led to the discovery of VIRGOHI21, the first galaxy to be detected
with gas, large amounts of the mysterious dark matter but no visible
stars. By discovering more objects like VIRGOHI21 scientist hope to answer
one of the greatest cosmological questions: if, as theoreticians predict,
matter in the Universe is mainly dark then where does is all reside? The
AGES team hopes that the survey will reveal exactly how much matter is
hidden in dark galaxies and determine whether current theories are
correct.

IMAGES

[Image 1:
http://www.ras.org.uk/images/stories...darkgalaxy.jpg (65KB)]
Caption: Digitized Sky Survey image of the candidate dark galaxy.

[Image 2:
http://www.ras.org.uk/images/stories/press/NGC4276.jpg (58KB)]
Caption: Galaxy NGC4276, which is about the same mass and at a similar
distance to the new candidate dark galaxy and should be similar in
appearance.

For images of the region near NGC1156, see:
http://www.naic.edu/~ages/a2048/first_results.html

FURTHER INFORMATION

AGES

AGES is a sub-group of the Extragalactic Arecibo L-Band Feed Array (EALFA)
consortium. The group aim to make use of the newly installed ALFA on the
Arecibo Telescope to conduct medium-senstivity observations of specific
regions of interest on the sky, focussing on galaxy groups and individual
galaxies.

AGES is a collaboration between Cardiff University, Lafayette College,
Cornell University, Queens University, Observatoire Astronomique de
Marseille- Provence, University of Moscow, University of Oregon,
Swinbourne University, Australia Telescope National Facility, Australian
National University, Space Telescope Science Institute, Wise Observatory,
European Southern Observatory, Mexico, Arecibo Observatory, University of
Michigan, University of Milan, National Radio Astronomy Observatory,
University of Colorado, Astronomical Observatory of Rome, University of
New Mexico, University of Massachusetts

NOTES FOR EDITORS

Royal Astronomical Society's National Astronomy Meeting

The 2006 RAS National Astronomy Meeting is hosted by the University of
Leicester. It is sponsored by the Royal Astronomical Society, the UK
Particle Physics and Astronomy Research Council (PPARC), the University of
Leicester and the National Space Centre, Leicester.

CONTACTS

Mr Robbie Auld
School of Physics and Astronomy, Cardiff University
5, The Parade, Cardiff, CF24 3YB, Wales, UK
Phone: +44 (0)29 20 876992

Dr Jonathan Davies
School of Physics and Astronomy, Cardiff University
5, The Parade, Cardiff, CF24 3YB, Wales, UK
Phone: +44 (0)29 20 875255