Superwind discovered spreading star dust across the Universe 
      A team of astronomers, led by the University of Durham, has discovered the 
      aftermath of a spectacular explosion in a galaxy 11.5 billion light years 
      Superwind discovered spreading Star Dust across the Universe
      A team of astronomers, led by the University of Durham, has discovered the 
      aftermath of a spectacular explosion in a galaxy 11.5 billion light years 
      away. Their observations, reported today (14th July 2005) in the journal 
      Nature provide the most direct evidence yet of a galaxy being almost torn 
      apart by explosions that produce a stream of high-speed material known as 
      "Superwinds".  The observations were made using the 4.2 metre William 
      Herschel Telescope on La Palma in which the UK is a major stakeholder. 

      Through Superwinds, galaxies are thought to blast a significant part of 
      their gas into intergalactic space at speeds of up to several hundred 
      miles per second. The driving force behind them is the explosion of many 
      massive stars during an intense burst of star formation early in the 
      galaxy's life, possibly assisted by energy from a super massive black hole 
      growing at its heart.

      Superwinds are vital to the theory of galaxy formation for several 
      reasons: firstly, they limit the sizes of galaxies by preventing further 
      star formation - without them theoretical models indicate far more very 
      bright galaxies than are actually seen in the Universe today. Secondly, 
      they carry heavy elements - Star dust - far from their production sites in 
      stars out into intergalactic space, providing raw material for planets and 
      life across the Universe. Whilst the theories predicted Superwinds of this 
      kind existed, previously observed examples were much smaller phenomena in 
      nearby galaxies. These observations provide some of the most direct 
      evidence yet for the existence of large-scale, galaxy-wide superwinds so 
      far back in the history of the Universe.

      The discovery of the Superwind was made by observing the gas in the  halo 
      of a galaxy (known as "LAB-2"), which at over 300,000 light years across 
      is about three times larger than the disk of our own Milky Way galaxy. The 
      astronomers discovered that light from hot glowing hydrogen gas is dimmed 
      in a very specific way across the entire galaxy.

      "We believe that the dimming is caused by a shell of cooled material which 
      has been swept-up from the surroundings by a galaxy-wide Superwind 
      explosion," said Dr. Richard Wilman of the University of Durham. "Based on 
      the uniformity of the absorption across the galaxy, it appears that the 
      explosion was triggered several hundred million years earlier. This allows 
      time for the gas to cool and to slow down from its high ejection speed, 
      and thus to produce the absorption. As we see it, the shell is probably a 
      few hundred thousand light years in front of its parent galaxy," added Dr. 

      Astronomers have long been puzzled about why key elements for the 
      formation of planets and ultimately life (such as carbon, oxygen and iron) 
      are so widely distributed throughout the Universe; only 2 billion years 
      after the Big Bang, the remotest regions of intergalactic space have been 
      enriched with them. The Superwind observed in this galaxy shows how such 
      blast waves can travel through space carrying the elements formed deep 
      within galaxies.

      Crucial to the discovery and its interpretation was the ability to obtain 
      detailed information on the gas in two-dimensions across the whole galaxy. 
      This was made possible by a technique known as integral field 
      spectroscopy, which is only just reaching maturity on the world's largest 

      Dr Joris Gerssen, a key member of the Durham team, explains, "Most 
      astronomical spectroscopy is performed by placing a small aperture, or a 
      narrow slit on the target, which for complex, extended sources such as 
      this galaxy gives a rather incomplete picture".

      To overcome this the astronomers used an integral field spectrograph 
      called 'Sauron' for a large survey of nearby galaxies, built at the 
      Observatoire de Lyon by a collaboration of French, Dutch and UK 

      Dr Gerssen added," "Sauron is truly unique and its high efficiency means 
      that it can more than hold its own against instruments on the world's 
      largest telescopes, some twice the size of the William Herschel Telescope. 
      Nevertheless, the sheer distance of our target galaxy meant that Sauron 
      had to stare at it for over 15 hours in order to make this discovery".

      "Sauron has provided us with the best evidence so far for an extensive 
      outflow from a galaxy undergoing a huge starburst. These measurements are 
      among the first steps towards understanding the physics of galaxy 
      formation.," commented Prof. Roger Davies, University of Oxford, one of 
      the institutes involved on Sauron," and we look forward to using similar 
      two-dimensional spectrographs being built for 8m telescopes; these will 
      probe the galaxy formation process to even earlier times."

      To date, observational evidence for Superwinds in young galaxies in the 
      distant Universe has been largely indirect and circumstantial; efforts 
      have focussed on searching for their subtle statistical signatures in 
      large surveys of galaxies and intergalactic gas.

      According to Prof. Richard Bower, from the University of Durham's 
      Institute of Computational Cosmology who initiated the research, 
      "Astronomers have observed high-speed outflows in distant star-forming 
      galaxies for several years, but never before have we been able to gauge 
      their true scale from observations of a single galaxy. By taking advantage 
      of the highly extended emission source of this galaxy, we can see the 
      outflow as a kind of silhouette against the whole galaxy. This suggests 
      that Superwinds are truly galaxy-wide in scale, and that they really are 
      as important as our theories require."


      Peter Barratt - PPARC Press Office. Tel: 01793 442025. 
      Dr. Richard Wilman, Department of Physics University of Durham. Tel: 0191 
      334 3792. 

      The full listing of authors and their affiliations for this Nature paper 
      is as follows:
      R. J. Wilman, J. Gerssen, R. G. Bower, S. L. Morris - Department of 
      Physics, University of Durham, South Road, Durham DH1 3LE, UK
      R. Bacon - CRAL-Observatoire, 9 Avenue Charles-Andri, 69230 
      Saint-Genis-Laval, France.
      P. T. de Zeeuw - Leiden Observatory, Niels Bohrweg 2, 2333 CA Leiden, The 
      R. L. Davies  - Astrophysics, University of Oxford, Keble Road, Oxford, 
      OX1 3RH, UK.

      William Herschel Telescope

      The Isaac Newton Group of Telescopes (ING) is an establishment of the 
      Particle Physics and Astronomy Research Council (PPARC) of the United 
      Kingdom, the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) 
      of the Netherlands and the Instituto de Astrofmsica de Canarias (IAC) in 
      Spain. The ING operates the 4.2-metre William Herschel Telescope, the 
      2.5-metre Isaac Newton Telescope, and the 1.0-metre Jacobus Kapteyn 
      Telescope. The telescopes are located in the Spanish Roque de Los 
      Muchachos Observatory on La Palma, Canary Islands, which is operated by 
      the Instituto de Astrofmsica de Canarias (IAC).