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Astrophysicists discover earliest known ‘starburst’ galaxy in Universe
University of Sussex astronomers using the Herschel Space Observatory are part of an international team that has discovered a distant star-forming galaxy that challenges the current theories of galaxy evolution.
Seen when the Universe was less than a billion years old (880 million years) the galaxy, known only as “HFLS3”, is forming stars at a much faster rate than should be possible according to existing predictions. In the infant Universe, galaxies should have been forming stars at a much slower rate than is observed in HFLS3.
HFLS3 is so distant that the light we see from it has taken 13 billion years to get to Earth.
The Herschel observatory1 has been surveying the distant cosmos and finding hundreds of thousands of distant galaxies. Images produced by Herschel show how fast these distant galaxies are forming stars.
By determining the ages of the galaxies, astronomers have been building up a cosmic timeline of star formation, searching for when the first massive galaxies started churning out stars.
University of Sussex PhD student Peter Hurley, Dr Isaac Roseboom, Dr Anthony Smith, Dr Lingyu Wang and Professor Seb Oliver, who leads the HerMES2 survey that found the galaxy, analysed data from Herschel and built the HFLS3 galaxy as a computer model to discover what conditions are like in the galaxy.
Peter says: “The stars being born in HFLS3 heat up the surrounding material within the galaxy. This material contains gas molecules such as carbon monoxide and water, which emit their own unique signatures when heated. By comparing the telescope observations with models, we can gain a better understanding of the conditions within this extreme galaxy.”
The galaxy “HFLS3” was first seen as a small red dot in the Herschel images, and its colour is what first intrigued the team because red galaxies might be very distant.
Further investigations using optical and near-infrared telescopes the Gran Telescopio Canarias in the Canary Islands and the Keck Telescope in Hawaii helped to rule out any other effects that might cause the HFLS3 galaxy to look so bright.
It was observations with radio and millimetre-wave telescopes, such as the Plateau de Bure Interferometer in the French Alps, which determined that this tiny galaxy, only around one twentieth the size of our Milky Way, is seen at such an immense distance. These additional observations also showed that HFLS3 is incredibly rich in carbon, nitrogen and oxygen, forming compounds such as carbon monoxide, water and ammonia. These compounds reveal the physical processes at work in this distant galaxy.
Combined with the Herschel observations, these measurements allow the astronomers to deduce that this tiny star factory is producing stars around two thousand times faster than our own Milky Way, making it a type of galaxy known as a “starburst”. Environments like this do not exist on galaxy-wide scales in the Universe today.
Professor Oliver says: “We’ve shown that Herschel data can find these extreme examples. “The next step is to sift through the Herschel data more carefully, and try to deduce just how common such galaxies were in the early Universe. I am also very pleased that a Sussex PhD student has been able to make an important contribution to this work.”
Jamie Bock (Caltech, USA), who co-leads the HerMES survey with Professor Oliver, says: "This galaxy is just one spectacular example, but it's telling us that early star formation like this is possible."
Dominik Riechers (Cornell University, USA), who led the HFLS3 study, says: “Looking for the first examples of these massive star factories is like searching for a needle in a haystack. We were hoping to find a galaxy at such vast distances, but we could not expect that they even existed that early on in the Universe."
Notes for editors
1. On Sussex Home Page and this press release: Artist's impression of galaxy HFLS3, courtesy of the European Space Agency
2. Full caption for Herschel image et al:
The galaxy “HFLS3” was found initially as a small red dot in Herschel submillimetre images (main image, and panels on right). Subsequent observations with ground-based telescopes, ranging from optical to millimetre-wave (insets) showed that there are two galaxies appearing very close together. They are at very different distances, however, with one of them, seen in millimetre-wave (inset, blue) being so distant that we are seeing it as it was when the Universe was just 880 million years old, and was forming stars 1000 times faster than our Milky Way galaxy.
‘A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34’ by D. Riechers et al (2013) Nature, 18 April 2013. UK-based authors are Peter Hurley, Seb Oliver, Isaac Roseboom, Anthony Smith, Lingyu Wang (University of Sussex); Dave Clements, Ashley Hyde (Imperial College London); Rob Ivison, Edo Ibar (UK Astronomy Technology Centre); Vinodiran Arumugam, James Dunlop, Alasdair Thomson (University of Edinburgh); Scott Chapman, Eduardo Gonzalez Solares (University of Cambridge); Mat Page (Mullard Space Science Laboratory)
The observations were made of a small area of sky which lies in the constellation of Draco. The Herschel data was taken as part of the HerMES project, which issued its first data release in April 2012. Other facilities used were the Combined Array for Research in Millimeter-wave Astronomy (CARMA); Caltech Submillimeter Observatory (CSO); Plateau de Bure Interferometer (PdBI); Jansky VLA (JVLA); Submillimeter Array (SMA); IRAM 30-m telescope; William Herschel Telescope (WHT); Gran Telescopio Canarias (GTC); Keck Telescope; the Wide Field Infrared Survey Explorer (WISE), and the Spitzer Space Telescope.
Herschel is a European Space Agency space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. It was launched in May 2009. The Herschel programme forms a key part of the UK Space Agency’s space science programme. The SPIRE instrument was used in this work, which was led by the UK.
For further information about the HFLS3 project see the ESA Herschel web site.
HerMES is the Herschel Multi-tiered Extragalactic Survey, an astronomical project to study the evolution of galaxies in the distant Universe. It is the largest project on ESA's Herschel Space Observatory. The project is carried out by a large team, made up primarily of people who built one of the instruments on Herschel called SPIRE. Hermes is also the Olympian messenger god, ruler of travelers, boundaries, weights and measures.
HerMES has mapped large regions of the sky using cameras that are sensitive to infrared radiation. We have discovered over 100 thousand galaxies. The light from most of these galaxies will have taken more than 10 billion years to reach us, which means we see them as they were 3 to 4 billion years after the big bang. Since the cameras are detecting infrared radiation they see star formation that is hidden from conventional telescopes. We expect that our cameras will catch many of the galaxies at the moment they are forming most of their stars. HerMES is led by Prof. Seb Oliver (University of Sessex) and Dr. Jamie Bock (Caltech).
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