Early Galaxies Were Ahead of Their Time

©ESA et al

HFLS3

Astronomers using Europe's Herschel Space Observatory have discovered a distant galaxy that challenges the current theories of galaxy evolution. Seen when the universe was less than a billion years old, it is forming stars at a much faster rate than should be possible according to existing predictions.

This particular galaxy, known only as "HFLS3," is so distant that the light we see has taken 13 billion years to get to Earth. We see it as it was when the universe was only 880 million years old, long before current theories of galaxy evolution predict that such a galaxy should have existed. In the infant Universe, galaxies should have been forming stars at a much slower rate than is observed in HFLS3.

Herschel has been surveying the distant cosmos, finding hundreds of thousands of distant galaxies. By looking at sub-millimeter light, Herschel is revealing how fast these distant galaxies are forming stars, and by determining the ages of the galaxies, astronomers are building up a cosmic timeline of star formation, searching for when the first massive galaxies started churning out stars.

"Looking for the first examples of these massive star factories is like searching for a needle in the haystack," says Dominik Riechers, Cornell University, who led the investigation. "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."

The galaxy "HFLS3" was seen as a small red dot in the Herschel images, and its color is what first intrigued the team. "This galaxy gained our attention because it was bright, yet very red, compared to others like it," says Dave Clements, Imperial College London. "But while Herschel is great at highlighting these galaxies, we need to use other telescope to investigate further," he adds.

The first step was to rule out any other effects that could cause the galaxy to look so bright. Using optical and near-infrared telescope, such as the Gran Telescopio Canarias in the Canary Islands and the Keck Telescope in Hawaii, the faint light from a much closer galaxy was seen. Although it lies in almost the same place in the sky, this relatively nearby imposter could not account for the brightness of HFLS3 in the Herschel images.

It was observations with radio and millimeter-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.

"The stars being born in HFLS3 heat up the surrounding material within the galaxy.," explained Peter Hurley, University of Sussex. "This material contains gas molecules such as carbon monoxide and water, which emit their own unique signatures when heated. By comparing the observations with models, we can gain a better understanding of the conditions within this extreme object."

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.

"This galaxy is just one spectacular example, but it's telling us that early star formation like this is possible," explains Jamie Bock, Caltech, and one of the leaders of HerMES survey which originally found this galaxy.

"We've shown that Herschel data can find these extreme examples," says Seb Oliver, University of Sussex, and the other leader HerMES. "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," he concludes.

Contact s :
Julia Short
Press Officer
UK Space Agency
+44 (0)1793 418069
julia.short@ukspaceagency.bis.gsi.gov.uk

Dr. Chris North
UK Herschel Outreach Officer
School of Physics and Astronomy
Cardiff University, UK
+44 (0)2920 870 537
chris.north@astro.cf.ac.uk

Image:
http://www.bis.gov.uk/assets/ukspaceagency/images-2013/fls_HFLs3_zoom_final

Caption:
The galaxy "HFLS3" was found initially as a small red dot in Herschel submillimeter images (main image, and panels on right). Subsequent observations with ground-based telescopes, ranging from optical to millimeter-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 millimeter-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.

Credit:

ESA/Herschel/HerMES/IRAM/GTC/W. M. Keck Observatory

Reference:

"A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34" by D. Riechers et al. (2013), Nature, http://www.nature.com/nature/journal/v496/n7445/full/nature12050.html

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 Center); 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:

Herschel is an ESA 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 program forms a key part of the UK Space Agency's space science program. The SPIRE instrument which was used in this work, was led by the UK.

SPIRE:

The SPIRE (Spectral and Photometric Imaging Receiver) instrument has been developed by an international consortium. It is led by a Principal Investigator from Cardiff University. The SPIRE instrument contains an imaging photometer (camera) and an imaging spectrometer. The camera operates in three wavelength bands centered on 250, 350 and 500 microns, and so can make images of the sky simultaneously in three sub-millimeter colors. The SPIRE instrument has been built, assembled and tested in the UK at The Rutherford Appleton Laboratory in Oxfordshire by an international consortium from Europe, US, Canada and China.

HerMES:

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).

UK Space Agency:

The UK Space Agency is at the heart of UK efforts to explore and benefit from space. It is responsible for all strategic decisions on the UK civil space program and provides a clear, single voice for UK space ambitions. The UK Space Agency is responsible for ensuring that the UK retains and grows a strategic capability in the space-based systems, technologies, science and applications. It leads the UK's civil space program in order to win sustainable economic growth, secure new scientific knowledge and provide benefits to all citizens. The UK Space Agency co-ordinates UK civil space activity; encourages academic research; supports the UK space industry; raises the profile of UK space activities at home and abroad; increases understanding of space science and its practical benefits; inspires our next generation of UK scientists and engineers; licenses the launch and operation of UK spacecraft; and promotes co-operation and participation in the European space program.

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