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An international team of more than 200 astronomers from 18 countries has released the first phase of a new large-scale sky radio survey with unprecedented sensitivity, using the LOFAR (Low Frequency Array) telescope. The survey reveals hundreds of thousands of galaxies not yet detected, shedding new light on many areas of research, including black hole physics and the evolution of clusters of galaxies. A special issue of Astronomy and astrophysics is devoted to the first 26 research articles describing the survey and its first results.
Radioastronomy reveals processes in the universe that can not be seen with optical instruments. In this first part of the sky, LOFAR observed a quarter of the northern hemisphere at low radio frequencies. At this point, about 10% of this data has been made public. It maps 300,000 sources, almost all galaxies from the distant universe; their radio signals have traveled billions of light years to reach Earth.
Black holes
Huub Röttgering, University of Leiden (The Netherlands): "If we take a radio telescope and look up to the sky, we will see mainly emissions from the immediate environment of huge black holes." With LOFAR, we hopefully can answer the fascinating question: Where do these black holes come from? "Researchers know that black holes eat badly. When the gas falls on them, they emit jets of visible material at radio wave lengths.
Philip Best, University of Edinburgh (United Kingdom), says: "LOFAR has a remarkable sensitivity, which allows us to see that these jets are present in all the most gigantic galaxies, which means that their black holes do not stop never eat. "
Clusters of galaxies
Clusters of galaxies are sets of hundreds to thousands of galaxies. It has been known for decades that the fusion of two clusters of galaxies can produce radio broadcasts spanning millions of light years. It is thought that this emission comes from accelerated particles during the melting process. Amanda Wilber, University of Hamburg (Germany), "With radio observations, we can detect radiation from the thin medium between galaxies, which is generated by energy shocks and turbulence." LOFAR allows us to detect much more from these sources and understand what is feeding them. "
Annalisa Bonafede, University of Bologna and INAF (Italy), says: "What we are starting to see with LOFAR is that in some cases, clusters of galaxies that do not merge can also show this emission, although at a very low level undetectable. This discovery teaches us that, in addition to fusion events, there are other phenomena that can trigger particle acceleration on a very large scale. "
Magnetic fields
"Magnetic fields invade the cosmos and we want to understand how that happened." Measuring magnetic fields in an intergalactic space can be difficult because they are very small, but the unprecedented accuracy of LOFAR measurements has allowed us to to measure the effect of magnetic fields on the radio waves of a giant radio galaxy 11 million light-years show how we can use LOFAR to help us understand the origin of the cosmic magnetic fields, "says Shane O" Sullivan, University of Hamburg.
High quality images
The creation of low-frequency radio sky maps takes a lot of computing and telescope time and requires data analysis by large teams. "LOFAR produces huge amounts of data We need to process the equivalent of 10 million DVDs LOFAR surveys have recently been made possible by a mathematical breakthrough in the understanding of interferometry" says Cyril Tasse, Observatoire de Paris – Radio astronomy station in Nançay (France).
"We have worked with SURF in the Netherlands to efficiently transform huge amounts of data into high quality images, which are now public and will allow astronomers to study the evolution of galaxies with unprecedented details. "said Timothy Shimwell, Netherlands. Radioastronomy Institute (ASTRON) and Leiden University.
The SURF data and computing center at SURFsara in Amsterdam is 100% renewable energy and hosts more than 20 petabytes of LOFAR data. "This is more than half of all data collected to date by the LOFAR telescope, the largest collection of astronomical data in the world, and the processing of these huge data sets is a daunting task. for scientists was treated in less than a year using the high-throughput computing cluster (Grid) and its expertise, "says Raymond Oonk (SURFsara).
LOFAR
The LOFAR telescope, the low frequency network, is unique in that it can map the sky down to the smallest details at meter wavelengths. LOFAR is operated by ASTRON in the Netherlands and is considered the largest telescope in the world. "This map of the sky will be a wonderful scientific legacy for the future, and it tells the LOFAR designers that this telescope works so well," said Carole Jackson, ASTRON's general manager.
The next step
The 26 research articles of the special issue of Astronomy and astrophysics were made with only the first two percent of the sky. The team's goal is to create sensitive, high-resolution images of the entire northern sky, which will reveal a total of 15 million radio sources. "Imagine some of the discoveries we could make along the way, and I'm looking forward to it," says Jackson. "And among these, there will be the first massive black holes that formed when the universe was only a" baby ", with an age of a few percent of its age ", adds Röttgering.
Explore further:
Clusters of galaxies in collision
More information:
T. W. Shimwell et al. The LOFAR sky survey of two meters, Astronomy and astrophysics (2018). DOI: 10.1051 / 0004-6361 / 201833559
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