Lofar’s record-sharp image gives astronomers a new view of galaxy M 82

An international team of astronomers led from Chalmers University of Technology has used the giant radio telescope Lofar to create the sharpest astronomical image ever taken at very long radio wavelengths. Made by observing simultaneously from four countries, including Sweden, the image shows the glowing centre of the galaxy Messier 82 – and many bright remnants of supernova explosions.

Astronomers have taken the sharpest image yet of the sky at very long radio wavelengths. The image shows the centre of the galaxy Messier 82 (M 82), also known as the Cigar Galaxy, 11.5 million light years from Earth. M 82 is forming stars much faster than our galaxy, the Milky Way, and is a favourite object for many astronomers who investigate the evolution of stars and galaxies.

In images taken in visible light, M 82 is a riot of stars, gas and dust. Lofar shows us a completely different scene.

– In Lofar’s new extremely sharp image we’re seeing a collection of bright spots, which are most likely supernova remnants, explains Eskil Varenius at Chalmers University of Technology, who led the international team of scientists behind the new image.

A supernova remnant is a shining shell of shock waves from an exploded star, ploughing into its surroundings. Supernova remnants are huge objects by everyday standards, much larger than the size of our own solar system, but look small from a distance.

– This galaxy is millions of light years away, and each remnant can be as little as a few light years across. We need extremely sharp images to study them, says Eskil Varenius.

The supernova remnants are embedded inside a huge, diffuse cloud of charged particles, or plasma, which absorbs radio waves from these sources. By investigating how different wavelengths pass through the plasma, scientists can learn more about how a gigantic star factory like M 82 works.

– We’re surprised that Lofar can see as many as 16 bright supernova remnants in M 82. This image can give us new clues to the structure of M 82 and why so many stars are being formed there, says John Conway, part of the team and director of Onsala Space Observatory where Sweden’s Lofar station is located.

This exciting image of M 82 is the first of many that Lofar and its international stations will be able to give us. The scientists are now working on new super-sharp Lofar images of other galaxies.

– Lofar is showing us the sky in a way that we’ve never seen before, and in in exquisite detail. This beautiful image is just a foretaste of what the telescope is capable of, says Mike Garrett, director of Astron, the Netherlands Institute for Radio Astronomy.

Caption: The centre of the galaxy M 82 at very long radio wavelengths (2.5 m/118 MHz [orange] and 1.9 m/154 MHz [blue]). The bright points are most likely supernova remnants. The image is about 3300 light years across.
Credit: E. Varenius/Onsala Space Observatory/Lofar collaboration

About Lofar

• Lofar (Low Frequency Array) is a radio telescope which consists of thousands of antennas spread across northern Europe with its core in the Netherlands. The telescope is uniquely sensitive to the very longest radio waves that can penetrate Earth’s atmosphere.
• Lofar is designed and built by ASTRON, the Netherlands Institute for Radio Astronomy. The International Lofar Telescope has 38 stations in the Netherlands, six in Germany, and one each in France, Sweden and the United Kingdom. Three further stations are under construction in Poland.
• Lofar is also a recognized science and technology pathfinder facility for the next-generation radio telescope, the Square Kilometre Array (SKA). Onsala Space Observatory represents Sweden, one of 11 member countries in the SKA Organisation.

About the research
The research is published in the paper Subarcsecond international LOFAR radio images of the M82 nucleus at 118 MHz and 154 MHz by E. Varenius et al., to be published shortly in Astronomy & Astrophysics. A version of the paper is available online at http://arxiv.org/abs/1411.7680

The team is comprised of researchers from Chalmers University of Technology in Sweden, University of Manchester in United Kingdom, Astron in the Netherlands, Max-Planck-Institut für Radioastronomie [MPIfR] in Germany, Instituto de Astrofísica de Andalucíain in Spain, Jagiellonian University in Poland, Royal Observatory Edinburgh in United Kingdom, Ruhr-Universität Bochum in Germany, Observatoire de Paris in France, INAF-Istituto di Radioastronomia in Italy, University of Hamburg in Germany, Radboud University in the Netherlands, Leiden University in the Netherlands, University of Oxford in United Kingdom, Open University and RAL in United Kingdom.

Contacts:

• Robert Cumming, astronomer and communications officer, Onsala Space Observatory, Chalmers University of Technology, Sweden, +46 31-772 5500, +46 70-493 31 14, robert.cumming@chalmers.se
• Eskil Varenius, Department of Earth and Space Sciences, Chalmers University of Technology, Sweden, +46 31-772 5500 or +46 706 755 341, eskil.varenius@chalmers.se