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New discovery sheds light on the ecosystem of young galaxies

Last Updated on Monday, 29 August 2011 20:57
Published on Monday, 29 August 2011 20:44
An international team of scientists, led by Michael Rauch from the Carnegie Observatories in California in the United States has discovered a distant galaxy that may help elucidate two fundamental questions of galaxy formation: How galaxies take in matter and how they give off energetic radiation. Their work will be published in the journal Monthly Notices of the Royal Astronomical Society.

 

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An image of the galaxy LDSS3 (within the red ellipse) from the Hubble Space telescope archive, that shows that the underlying galaxy is highly distorted, with extended stellar tails to the left and right. Credit: Michael Rauch / Carnegie Institution for Science / STScI
During the epoch when the first galaxies formed, it is believed that they radiated energy, which hit surrounding neutral hydrogen atoms and excited them to the point where they were stripped of electrons. This produced the ionized plasma that today fills the universe. But little is known about how this high-energy light was able to escape from the immediate surroundings of a galaxy, known as the galactic halo. The galaxies we observe today tend to be completely surrounded by gaseous halos of neutral hydrogen, which absorb all light capable of ionizing hydrogen before it has a chance to escape.

 

Rauch and his team, using the Magellan Telescopes at Las Campanas Observatory in Chile and archival images from the Hubble Space Telescope, discovered a galaxy (LDSS3) with an extended patch of light surrounding it. The objects appearance means that roughly half of the galaxy's radiation must be escaping and exciting hydrogen atoms outside of its halo.

The key to the escape of radiation can be found in the unusual, distorted shape of the newly observed galaxy. It appears that the object had recently been hit by another galaxy, creating a hole in its halo, allowing radiation to pass through.

"The loss of radiation during galactic interactions and collisions like the one seen here may be able to account for the re-ionization of the universe", Rauch said. "This galaxy is a leftover from a population of once-numerous dwarf galaxies. And looking back to a time when the universe was more dense, crashes between galaxies would have been much more common than today."

The new observation also helps scientists better understand the flow of inbound matter, from which a galaxy originally forms. In the present case, the escaping ionizing radiation illuminated a long train of incoming gas, which is feeding new matter into the galaxy. The existence of such structures had been predicted by theory, but they had not been seen previously because they barely emit any light of their own.

 


CONTACTS

 

Michael Rauch
Carnegie Observatories
Pasadena
California
United States
Tel: +1 (626) 304 0262
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7734 3307 x214
Mob: +44 (0)794 124 8035
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

 


FURTHER INFORMATION

 

The co-authors on this paper are George Becker and Martin Haehnelt from the Kavli Institute for Cosmology at Cambridge University, Jean-Rene Gauthier from The Kavli Institute for Cosmological Physics at the University of Chicago, Swara Ravindranath from the Inter-University Centre for Astronomy and Astrophysics, and Wallace Sargent from the Palomar Observatory at California Institute of Technology.

See http://carnegiescience.edu/news/new_discovery_sheds_light_ecosystem_young_galaxies

 

 


 

NOTES FOR EDITORS

The Carnegie Institution for Science

The Carnegie Institution for Science http://carnegiescience.edu is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

The Royal Astronomical Society

The Royal Astronomical Society (RAS, www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

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