Young galaxy is surprisingly efficient star-factory
13 May 2013 by hddbqtthcb.d hddbqtthcb.d
Astronomers have discovered an extremely distant galaxy that has one of the largest star-formation rates they have ever seen.
The new galaxy, called HFLS3, looks like a faint red smudge in images from the European Space Agency’s Herschel Multi-tiered Extragalactic Survey (HerMES). The images represent the galaxy producing new stars from gas and dust, which makes it a ‘starburst galaxy’.
“This particular galaxy got our attention because it was bright, and yet very red compared to others like it,” said Herschel researcher Dr Dave Clements from the Department of Physics at Imperial College London.
HFLS3 is one of tens of thousands of massive, star-forming galaxies that have been imaged as part of HerMES. The telescope has produced images of the galaxy as it was when the Universe was less than a billion years old.
The astronomers calculated that light from HFLS3 has travelled for almost 13 billion years across space and that by now, it may have expanded to be the same size as the largest known galaxies in the local universe.
This is the most active astronomers have seen such a young galaxy; it produces more than 2000 new stars each year and its rate of star formation is over a thousand times faster than the Milky Way’s. But according to current theories of galaxy evolution, galaxies as large as HFLS3 should not be present so soon after the Big Bang.
“The basic idea behind galaxy formation and evolution models is something called hierarchical clustering, whereby small young galaxies gradually merge together and accrete more material to become bigger. This takes time, so in the early stages of the universe you would expect nearly all galaxies to be small and to be forming stars at a fairly low rate because of this.” Clements told Laboratory News.
HFLS3’s existence challenges current theories of early galaxy formation, which predict that only much later will they reach such large masses.
“Exactly how this gets solved is unclear. There may be differences in the way stars form in dusty objects like HFLS3, compared to the more numerous, less star forming galaxies seen by Hubble, or it may be that some other things in the models need to be changed. The next step for us, already under way, is to find more sources like HFLS3 so we can properly characterise this population,” said Clements.
