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News  'Big baby' galaxy found in newborn Universe
The NASA/ESA Hubble Space Telescope and NASA’s Spitzer Space Telescope have teamed up to 'weigh' the stars in distant galaxies. One of these galaxies is not only one of the most distant ever seen, but it appears to be unusually massive and mature for its place in the young Universe. This has surprised astronomers because the earliest galaxies in the Universe are commonly thought to have been much smaller agglomerations of stars that gradually merged together later to build the large majestic galaxies like our Milky Way. "This galaxy appears to have 'bulked up' amazingly quickly, within a few hundred million years after the Big Bang," said Bahram Mobasher of the European Space Agency and the Space Telescope Science Institute, a member of the team that discovered the galaxy.
"It made about eight times more mass in terms of stars than are found in our own Milky Way today, and then, just as suddenly, it stopped forming new stars. It appears to have grown old prematurely."
The galaxy was detected using Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS), but at near-infrared wavelengths it is very faint and red.
It is also within the deepest survey from the Spitzer Space Telescope, the Great Observatories Origins Deep Survey (or GOODS). The galaxy is believed to be about as far away as the most distant galaxies and quasars now known. The light reaching us today began its journey when the Universe was only about 800 million years old.
Hubble's Advanced Camera for Surveys (ACS) does not see the galaxy at all, despite the fact that the HUDF is the deepest image ever taken in optical light. This indicates that the galaxy's blue light has been absorbed by travelling for millions of light-years through intervening hydrogen gas.
Spitzer's IRAC is sensitive to the light from older, redder stars, which should make up most of the mass in a galaxy, and the brightness of the galaxy suggests that it is very massive indeed. Previous observations have revealed evidence for mature stars in more ordinary, less massive galaxies at similar distances. Other joint Spitzer and Hubble analyses identify more galaxies nearly as massive as the Milky Way, seen when the Universe was less than one thousand million years old.
The new observations by Mobasher and his colleagues dramatically extend this notion of surprisingly mature ‘baby galaxies’ to an object which is perhaps ten times more massive, and seems to have formed its stars even earlier in the history of the Universe.
For more information: Bahram Mobasher Space Telescope Science Institute, Baltimore, USA Tel: +1 410 338 4974 E-mail: mobasher @ stsci.edu
Mark Dickinson
Lars Lindberg Christensen
Ray Villard
Gay Hill
Doug Isbell
Robert Tindol
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