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.
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.
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.
