Scientists have unveiled an exceptionally detailed map of the sky in radio waves, taken with the Europe-wide telescope Lofar. The map reveals 13.7 million cosmic sources, and provides the most complete census yet of actively growing supermassive black holes.
The newly released Lofar Two-metre Sky Survey (LoTSS-DR3) marks a major milestone in radio astronomy and international scientific collaboration. The results are described in a scientific paper in is the journal Astronomy & Astrophysics.
"This data release brings together more than a decade of observations, large-scale data processing and scientific analysis by an international research team,” says Timothy Shimwell, lead author and astronomer at Astron and Leiden University, Netherlands.
By observing the sky at low radio frequencies, the survey reveals a dramatically different view of the universe than that seen at optical wavelengths. Much of the detected emission arises from relativistic particles moving through magnetic fields, allowing astronomers to trace energetic phenomena such as powerful jets from supermassive black holes and galaxies undergoing extreme star formation across cosmic time.
“This map gives us a new look at the radio sky and at the history of the universe, and it almost makes you dizzy. Everywhere, Lofar sees traces of supermassive black holes, and now we have the opportunity to discover how much these active black holes have influenced the history of the universe”, says Cathy Horellou, astronomer at Chalmers.
Thanks to its remarkable detail, the survey has also exposed rare and elusive objects, including merging clusters of galaxies, faint supernova remnants, and flaring or interacting stars. The survey is already enabling hundreds of new studies across astronomy, offering fresh insights into the formation and evolution of cosmic structures, how particles are accelerated to extreme energies, and cosmic magnetic fields, while also making publicly available the most sensitive wide-area radio maps of the universe ever produced.
“Lofar can also measure polarisation very precisely. That means we can detect magnetic fields even in regions of the universe that are nearly empty”, says Cathy Horellou.
Photographer: LOFAR surveys collaboration
Transformative discoveries
While the scientific exploitation is only just beginning, the scale, sensitivity and resolution of the survey are already transforming radio astronomy, enabling new discoveries across a wide range of cosmic environments.
“We can study a diverse population of supermassive black holes and their radio jets at different stages of their evolution, showing how their properties depend not only on the black hole itself, but also on the galaxy and environment in which it resides,” says Martin Hardcastle of the University of Hertfordshire, UK.
The survey has also delivered robust measurements of star formation rates in millions of galaxies, showing how these rates vary with galaxy properties and across cosmic time. The data are being carefully searched for rare astrophysical phenomena, for example transient and variable radio sources, previously unknown supernova remnants, some of the largest and oldest known radio galaxies, and radio emission consistent with interactions between exoplanets and their host stars.
Technical innovation
Processing the data required the development of new techniques that accurately correct for severe distortions caused by the Earth’s ionosphere, and multiple high-performance computing systems.
“The volume of data we handled - 18.6 petabytes in total - was immense and required continuous processing and monitoring over many years, using more than 20 million core hours of computing time,” says Alexander Drabent of Thuringian State Observatory, Germany.
John Conway is professor of radio astronomy at Chalmers and director of Onsala Space Observatory.
“The survey is now open to everyone to explore. It is a gold mine for astronomers who want to understand the history of the universe, and it will stimulate completely new ways of digging into data using the latest in machine learning and AI”, he says.
More about the research
The survey is presented in the paper "The LOFAR Two-metre Sky Survey VII. Third Data Release", T. W. Shimwell et al. in Astronomy & Astrophysics.
Link to paper: doi: 10.1051/0004-6361/202557749.
Lofar (Low Frequency Array) is a revolutionary radio telescope designed and constructed by Astron, the Netherlands Institute for Radio Astronomy. Unlike traditional dish antennas, Lofar consists of thousands of simple antenna elements distributed across Europe, connected by fibre optic networks. Lofar’s unique design incorporates 38 stations in the Netherlands, and 14 international stations across Europe, forming one of the world’s largest, highest-resolution and most sensitive radio telescopes. Data from all antennas are combined using powerful computers to create images of the radio sky. Sweden’s Lofar station is located at Onsala Space Observatory, 45 km south of Gothenburg.
Lofar is operated by the Lofar European Research Infrastructure Consortium (LOFAR ERIC), which brings together institutions from the Netherlands, Germany, France, the United Kingdom, Poland, Italy, Sweden, Ireland, Latvia, and Bulgaria. LOFAR ERIC exemplifies international scientific cooperation, combining facilities, computing, and expertise across national boundaries.
Sky coverage: 19,035 square degrees (88% of northern sky)
Number of sources catalogued: 13,667,877
Frequency range: 120-168 MHz (wavelength ~2 metres)
Angular resolution: 6 arcseconds (9" below declination 10°)
Median sensitivity: 92 µJy/beam
Data volume: 18.6 petabytes processed; 590 TB final products
Observation time: 12,950 hours over 10.5 years
Processing power: ~20 million core hours
All LoTSS-DR3 data products are publicly available, including images and catalogues covering 19 035 square degrees (46% of the sky), polarization information, calibrated visibility data, and 590 terabytes of final products. These are available through:
https://lofar-surveys.org/dr3.html
https://doi.org/10.25606/SURF.lotss-dr3
An interactive version of the map is at this address: https://lofar-surveys.org/hips/LoTSS_DR3_high_hips/
Contact
Robert Cumming, astronomer and communicator, Onsala Space Observatory, Chalmers University of Technology, Sweden, robert.cumming@chalmers.se, +46704933114, +46317725500
Cathy Horellou, astronomer, Chalmers University of Technology, Sweden, cathy.horellou@chalmers.se
- Communications Officer, Onsala Space Observatory, Space, Earth and Environment
- Professor, Astronomy and Plasma Physics, Space, Earth and Environment
