Durham astronomers capture most detailed images of galaxies ever taken

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An international team of astronomers, led by Dr Leah Morabito of Durham University, have published the most detailed images ever seen of galaxies beyond our own. Using data collected by the Low Frequency Array (LOFAR), the new images push the boundaries of what we know about galaxies and super-massive black holes (SMBHs).

The LOFAR network is an array of more than 70,000 small antennae spread across Europe and is currently the largest radio telescope operating at the lowest frequencies observable from Earth. Together the antennae act as one large telescope that captures images at FM radio frequencies.

Unlike electromagnetic waves at higher frequencies, radio waves are not blocked by the clouds of dust and gas that can cover astronomical objects, such as the Earth’s atmosphere. Consequently, radio telescopes can operate from the surface of the Earth and be made much bigger than telescopes detecting shorter wavelengths, which often have to be placed in orbit.

Connecting multiple antennae in an array can make radio telescopes even larger. The LOFAR antennae are spread across Europe, with the majority located in the Netherlands. In standard operation, only signals from the antennae in the Netherlands are combined to create an array that is equivalent to a telescope with a diameter of 120km.

LOFAR antennae, Tammo Jan Dijkema via Flickr

The new images, however, use antenna stations located in Germany, Poland, France, Ireland, Latvia, Sweden and the United Kingdom as well, which are all partner countries of the International LOFAR Telescope. This allowed the diameter to increase to almost 2000km, resulting in a twenty-fold increase in resolution and the most detailed images of galaxies ever seen.

Conventional array antennae combine the signals from each antenna in real-time to produce images. However, LOFAR uses a new concept that involves collecting and digitising the signals from each antenna before they are transported to the central processer and combined into a single image. The antenna stations are connected by a high-speed fibre optic network, with an extremely powerful computer that processes the radio signals. To produce a single image, more than 13 terabits of raw data, the equivalent of more than three hundred DVDs, must be processed each second.

These new images will allow us to discover more about distant galaxies and the SMBHs at the centre of many of them. Another recent piece of research involving Durham University linked the feeding patterns of SMBHs to their size. The material accreted by SMBHs is released back into the cosmos as powerful jets and outflows of radiation. These jets are released at the frequency of radio waves, and it is these that the new high-resolution images have focused on.

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

Our aim is that this allows the scientific community to use the whole European network of LOFAR telescopes for their own science

Many more studies using these images and the LOFAR could now be made possible since the resulting Europe-wide array is a publicly-available data-processing pipeline that will allow astronomers from around the world to use LOFAR to make high-resolution images with relative ease.

Durham’s Dr Morabito 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.”

Image: L.K. Morabito; DESI Legacy Imaging Surveys. (An image showing what the radio emission looks like in LOFAR’s high resolution, using a galaxy from Morabito et al. (2021). The improved resolution means we can see all the jet details.)

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