Data on 400 million astronomical objects released in latest Dark Energy Survey update

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11 Jan 2018

Scientists on the Dark Energy Survey (DES), which includes many UK researchers, have this week released their first three years of data including information on about 400 million astronomical objects, ranging from distant galaxies billions of light years away from the Earth to stars in our own galaxy.
DES scientists are using this data to learn more about dark energy, the mysterious force believed to be accelerating the expansion of the universe. They presented some of their preliminary cosmological findings, which include the discovery of eleven new stellar streams, remnants of smaller galaxies torn apart and devoured by our Milky Way, in a special session held during the American Astronomical Society meeting in Washington, DC.

The UK has been involved in this international project from its conception, back in 2004, with STFC providing funding on behalf of the UK for what is the largest galaxy survey so far ever undertaken.
Professor Ofer Lahav from UCL, who chairs both the DES Advisory Board and the DES:UK consortium of seven universities, and co-directs UCL’s Centre for Doctoral Training in Data Intensive Science, said: “This data release is a milestone in this major galaxy survey. The best Cosmology and non-Cosmology results from DES are still to come from this and the final big data sets. This a great example of data intensive science."

The public release of the first three years of DES data fulfills a commitment scientists on the survey made to share their findings with the astronomy community and the public. The data covers the full DES footprint – about 5,000 square degrees, or one eighth of the entire sky – and include roughly 40,000 exposures taken with the Dark Energy Camera. The images correspond to hundreds of terabytes of data and are being released along with catalogs of hundreds of millions of galaxies and stars.
“There are all kinds of discoveries waiting to be found in the data,” said Dark Energy Survey Data Management Project Scientist Brian Yanny of the U.S. Department of Energy’s Fermi National Accelerator Laboratory. “While DES scientists are focused on using it to learn about dark energy, we wanted to enable astronomers to explore these images in new ways, to improve our understanding of the universe.”

One new discovery enabled by the data set is the detection of eleven new streams of stars
around our Milky Way. Our home galaxy is surrounded by a massive halo of dark matter, which exerts a powerful gravitational pull on smaller, nearby galaxies. The Milky Way grows by pulling in, ripping apart and absorbing these smaller systems. As stars are torn away, they form streams across the sky that can be detected using the Dark Energy Camera. Even so, stellar streams are extremely difficult to find since they are composed of relatively few stars spread out over a large area of sky.
Prior to the new discoveries by DES, only about two dozen stellar streams had been discovered.

DES plans one more major public data release, after the survey is completed, which will include nearly twice as many exposures as in this current release.
The DES data can be accessed online.
Looking to the future the plan is for the DES to be superseded by The Dark Energy Spectroscopic Instrument (DESI). The UK, through STFC support, will play an important role in helping to deliver what will be a massively multiplexed fibre-fed spectrograph that will make the next major advance in Fundamental Cosmology research in the timeframe 2019–2023.

Blanco Telescope Dome and Milky Way.