LOFAR Delivers Most Detailed-Ever Images Of Galaxies

MessageToEagle.com | August 29, 2021 | Astronomy | No Comments

Eddie Gonzales Jr. – MessageToEagle.com – The universe is awash with electromagnetic radiation, of which visible light comprises just the tiniest slice. From short-wavelength gamma rays and X-rays to long-wavelength microwave and radio waves, each part of the light spectrum reveals something unique about the universe.

A A compilation of the science results. Credit from left to right starting at the top: N. Ramírez-Olivencia et el. [radio]; NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), edited by R. Cumming [optical], C. Groeneveld, R. Timmerman; LOFAR & Hubble Space Telescope,. Kukreti; LOFAR & Sloan Digital Sky Survey, A. Kappes, F. Sweijen; LOFAR & DESI Legacy Imaging Survey, S. Badole; NASA, ESA & L. Calcada, Graphics: W.L. Williams.

The LOFAR network captures images at FM radio frequencies that, unlike shorter wavelength sources like visible light, are not blocked by the clouds of dust and gas that can cover astronomical objects. Regions of space that seem dark to our eyes, actually burn brightly in radio waves – allowing astronomers to peer into star-forming regions or into the heart of galaxies themselves.

The new images, made possible because of the international nature of the collaboration, push the boundaries of what we know about galaxies and supermassive black holes. A special issue of the scientific journal Astronomy & Astrophysics is dedicated to 11 research papers describing these images and the scientific results.

Better resolution by working together

The images reveal the inner workings of nearby and distant galaxies at a resolution 20 times sharper than typical LOFAR images. This was made possible by the unique way the team made use of the array.

The 70,000+ LOFAR antennae are spread across Europe, with the majority being located in the Netherlands. In standard operation, only the signals from antennae located in the Netherlands are combined and creates a ‘virtual’ telescope with a collecting ‘lens’ with a diameter of 120 km. By using the signals from all of the European antennae, the team has increased the diameter of the ‘lens’ to almost 2,000 km, which provides a twenty-fold increase in resolution.

Unlike conventional array antennae that combine multiple signals in real-time to produce images, LOFAR uses a new concept where the signals collected by each antenna are digitized, transported to central processor, and then combined to create an image. Each LOFAR image is the result of combining the signals from more than 70,000 antennae, which is what makes their extraordinary resolution possible.

Revealing jets and outflows from super-massive black holes

Super-massive black holes can be found lurking at the heart of many galaxies and many of these are ‘active’ black holes that devour in-falling matter and belch it back out into the cosmos as powerful jets and outflows of radiation. These jets are invisible to the naked eye, but they burn bright in radio waves and it is these that the new high-resolution images have focused upon.

Hercules A is powered by a supermassive black hole located at its centre, which feeds on the surrounding gas and channels some of this gas into extremely fast jets. Our new high-resolutions observations taken with LOFAR have revealed that this jet grows stronger and weaker every few hundred thousand years. This variability produces the beautiful structures seen in the giant lobes, each of which is about as large as the Milky Way galaxy. Credit: R. Timmerman; LOFAR & Hubble Space Telescope

Dr Neal Jackson of The University of Manchester, said: “These high-resolution images allow us to zoom in to see what’s really going on when super-massive black holes launch radio jets, which wasn’t possible before at frequencies near the FM radio band,”

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

A decade-long challenge

Even before LOFAR started operations in 2012, the European team of astronomers began working to address the colossal challenge of combining the signals from more than 70,000 antennae located as much as 2,000 km apart. The result, a publicly available data-processing pipeline, which is described in detail in one the scientific papers, will allow astronomers from around the world to use LOFAR to make high-resolution images with relative ease.

Dr Leah Morabito of Durham University, said: “Our aim is that this allows the scientific community to use the whole European network of LOFAR telescopes for their own science, without having to spend years to become an expert.”

Super images require supercomputers

The relative ease of the experience for the end-user belies the complexity of the computational challenge that makes each image possible. Because LOFAR doesn’t just ‘take pictures’ of the night sky, it must stitch together the data gathered by more than 70,000 antennae, which is a huge computational task. To produce a single image, more than 13 terabits of raw data per second – the equivalent of more than three hundred DVDs – must be digitized, transported to a central processor, and then combined.

Frits Sweijen of Leiden University said: “To process such immense data volumes we have to use supercomputers. These allow us to transform the terabytes of information from these antennas into just a few gigabytes of science-ready data, in only a couple of days.”

Links to Arxiv (free) papers can be found here.

Written by Eddie Gonzales Jr. MessageToEagle.com Staff