The most detailed images of galaxies seen with LOFAR

After nearly a decade of work, an international team of astronomers has published the most detailed images ever of galaxies beyond our own, revealing their way of working in unprecedented detail. Images were generated using data collected by ASTRON generated and run low frequency array (LOFAR), a radio telescope consisting of a network of more than 70,000 small antennas spread across nine European countries, with a core in Exloo, the Netherlands. The results were the culmination of years of work by a team led by Dr. Leah Morabito of Durham University. The team was supported in the UK by Science and Technology Facilities Council (STFC).

Synthesis of scientific results. Credit left to right starting from top: N. Ramírez-Olivencia et el. [radio]; NASA, European Space Agency, Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), ed. cumming [optical]C. Groeneveld, R. Timmerman; Lovar and Hubble Space Telescope. cokriti. LOFAR & Sloan Digital Sky Survey, A. Kappes, F. Swijen; LOFAR & DESI Legacy Imaging Survey, S. Badole; NASA, ESA and Calcada, Graphics: W.L. Williams.

In addition to supporting scientific exploitation, STFC is also funding the UK’s participation in LOFAR, including costs for the upgrade and operation of the LOFAR terminal in Hampshire.

Unveil a hidden world of light in HD

The universe is full of electromagnetic radiation, and visible light is only the smallest part of it. From short-wavelength gamma rays and X-rays to microwaves and long-wavelength radio waves, every part of the light spectrum reveals something unique about the universe.

The LOFAR network creates images at FM radio frequencies which, unlike shorter wavelength sources such as visible light, are not obscured by the clouds of dust and gas that can cover astronomical objects. Regions of space that appear dark to our eyes actually burn brightly in radio waves – allowing astronomers to see regions of star formation or the cores of galaxies themselves.

The new images, made possible by international cooperation, push the boundaries of what we know about galaxies and supermassive black holes. A special issue of the scientific journal Astronomy and astrophysics dedicated to 11 Research Papers Describe these images and scientific findings.

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Radio systems revealed by LOFAR. credit: LK Morabito; LOFAR KSP Surveys.

Better accuracy through collaboration

The images show the interior of near and far galaxies at a resolution 20 times higher than typical LOFAR images. This is made possible through the team’s unique use of the matrix.

More than 70,000 LOFAR antennas are scattered throughout Europe, mostly in the Netherlands. In normal use, only signals from antennas located in the Netherlands are combined, creating a “virtual” telescope with a collecting lens of 120 km in diameter. Using signals from all European antennas, the team increased the diameter of the “lens” to nearly 2,000 kilometers, increasing the accuracy by 20 times.

Unlike traditional array antennas that collect multiple signals in real time to produce images, LOFAR uses a new concept where the signals collected by each antenna are digitized, transmitted to a central processor and then combined to create an image. Each LOFAR image is the result of a combination of signals from more than 70,000 antennas, allowing for exceptional resolution.

The radio galaxy Hercules A is known for its massive jet streams, driven by a central supermassive black hole. credit: R. Timmerman; Lovar and Hubble Space Telescope.

Making jets of supermassive black holes visible

Supermassive black holes lie at the heart of many galaxies, many of which are “active” black holes that gobble up falling matter and spit it back into the universe in powerful jets. These jets are invisible to the naked eye, but they burn brightly in radio waves and these are the jets that the new high-resolution images have focused on.

Doctor. Neil Jackson from the University of Manchester said: “These high-resolution images allow us to zoom in and see what really happens when supermassive black holes emit radio jets, which were not previously possible at frequencies close to the FM radio range.

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The team’s work forms the basis for nine scientific studies that reveal new information about the internal structure of radio jets in a variety of different galaxies.

Ten year challenge

Even before LOFAR became operational in 2012, the team of European astronomers began working on the daunting challenge of combining signals from more than 70,000 antennas, which are separated by up to 2,000 kilometers. The result, a publicly available data processing pipeline, detailed in a scientific paper, will allow astronomers around the world to use LOFAR to create high-resolution images with relative ease.

Doctor. “Our goal is that this will allow the scientific community to use the entire European network of LOFAR telescopes for their science, without having to spend years becoming experts,” said Leah Morabito of Durham University.

Super photos require supercomputers

The relative ease of the end user experience belies the complexity of the computational challenge that makes every image possible. LOFAR not only takes “pictures” of the night sky, it has to assemble data collected by more than 70,000 antennas, a huge computational task. To produce a single image, more than 13 terabytes of raw data per second – the equivalent of more than 300 DVDs – must be digitized, transmitted to a central processor and then combined.

Frits Swegen from Leiden University: “To process such huge amounts of data, we have to use supercomputers. These allow us to convert terabytes of information from these antennas into a few gigabytes of data ready for science in a few days.” Source: Astro.

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