Astronomers detect hundreds of thousands of previously unknown galaxies

An international team of more than 200 astronomers from 18 countries, including researchers from the University of Oxford Hintze Centre for Astrophysical Surveys, has published the first phase of the survey at unprecedented sensitivity using the Low Frequency Array (LOFAR) telescope.

Radio astronomy reveals processes in the Universe that we cannot see with optical instruments. In this first part of the sky survey, LOFAR observed a quarter of the northern hemisphere at low radio frequencies. Today around ten percent of that data is being made public. It maps three hundred thousand sources, almost all of which are galaxies in the distant Universe; their radio signals have travelled billions of light years before reaching Earth.

Dr Leah Morabito, a Hintze fellow in Oxford Astrophysics, said: ‘We will be able to identify hidden black holes, study individual clouds of star formation in nearby galaxies, and understand what jets from black holes look like in the most distant galaxies.’

The energy output in these radio jets plays a crucial role in controlling the conversion of gas into stars in their surrounding galaxies.

Clusters of galaxies are ensembles of hundreds to thousands of galaxies. It has been known for decades that when two clusters of galaxies merge, they can produce radio emission spanning millions of light years. This emission is thought to come from particles that are accelerated during the merger process. New research using LOFAR is beginning to show this emission at previously undetected levels from clusters of galaxies that are not merging. This means that there are phenomena other than merger events that can trigger particle accelerations over huge scales.

LOFAR produces enormous amounts of data. The equivalent of ten million DVDs of data has been processed to create the low-frequency radio sky map. The survey was made possible by a mathematical breakthrough in the way we understand interferometry.

The LOFAR telescope is unique in its capabilities to map the sky in fine detail at metre wavelengths and is considered to be the world’s leading telescope of its type. The European network of radio antennas spans seven countries and includes the UK station at STFC RAL Space’s Chilbolton Observatory in Hampshire.

The signals from all of the stations are combined to make the radio images. This effectively gives astronomers a much larger telescope than it is practical to build - and the bigger the telescope, the better the resolution. The first phase of the survey only processed data from the central stations located in the Netherlands, but UK astronomers are now re-processing the data with all of the international stations to provide resolution twenty times better.

The team aims to make sensitive high-resolution images of the whole northern sky, which will reveal 15 million radio sources in total.

Dr Leah Morabito, added: ‘This extra phase of the survey will be truly unique in the history of radio astronomy, and who knows what mysteries we'll uncover?’

The Hintze Centre for Astrophysical Surveys, founded in 2014, is a group of research fellows and graduate students in the Astrophysics section of the Physics department. It hosts the twice yearly Hintze lectures. The Centre is funded by the Hintze Family Charitable Foundation.