A network of telescopes that has spent years looking into deep space has finally delivered some of the most gloriously detailed images we have seen of other galaxies.
These images are not only spectacularly beautiful, but reveal in unprecedented detail the inner workings of these giant cosmic objects, which give us a new insight into the workings of galaxies in general. The findings made so far have been published in a special issue of Astronomy and astrophysics.
The observations were made using the Low Frequency Array (LOFAR), the largest network of low frequency radio telescopes currently operating on Earth. It can combine observations from some 70,000 antennas spread across Europe using a technique called radio interferometry to make some of the most sensitive radio observations possible in the night sky.
This has provided us with incredible new information about the Universe, but the new observations go a step further, with a resolution 20 times higher than usual. This is due to the fact that standard LOFAR operations are only carried out using antennas in the Netherlands, where the collaboration is based.
On top: Radio footage reveals a huge wind blowing from the melting galaxies. (N. Ramírez-Olivencia et al .; NASA, ESA, Hubble Heritage Team (STScI / AURA) -ESA / Hubble Collaboration and A. Evans (UVA Charlottesville / NRAO / Stony Brook University); R. Cumming)
Since these antennas are spread over a region of 120 kilometers, this means that the aperture of the telescope is, in effect, about 120 kilometers in size. For the new observations, an international collaboration used the entire array across Europe, effectively a 2,000-kilometer (1,243-mile) radio telescope.
“Our goal is for this to allow the scientific community to use the entire European network of LOFAR telescopes for their own science, without having to spend years to become an expert,” said astronomer Leah Morabito of the University of Durham in the United Kingdom.
Nine papers in the special issue of Astronomy and astrophysics they are engaged in one of the most striking phenomena associated with galactic behavior: the jets of relativistic particles exploded in intergalactic space by supermassive black holes active in the centers of galaxies.
(A. Kappes)
They are invisible at optical wavelengths, but at radio wavelengths they shine, which means that radio images can give us an idea of how jets form and propagate.
It is known that once anything passes the critical threshold called the event horizon, nothing can escape the gravitational pull of a black hole. But the region around an active black hole is very dynamic. The material is spun on a disk that surrounds the black hole and climbs in as if water were flowing down a drain.
From the inner edge of this accretion disk, a small amount of swirling material is somehow wrapped around the outside of the event horizon toward the poles, where it is launched at speeds that are a significant percentage of light speed. Scientists believe that the magnetic field lines around the black hole act as a synchrotron, accelerating these particles to produce relativistic velocities.
This is what distant jets look like at very low frequencies. (C. Groeneveld)
However, there are many things we don’t understand about this process, and new LOFAR data helps fill in the missing pieces.
“These high-resolution images allow us to zoom in to see what really happens when supermassive black holes launch radio beams, which was previously not possible at frequencies close to the FM radio band,” explained astronomer Neal Jackson of the University of Manchester in the United Kingdom.
The galaxies analyzed include 3C 293, a galaxy with huge, peculiar radio lobes that suggest interrupted ray flow. The researchers concluded that the galaxy has experienced multiple periods of activity due to jet interruptions and intermittent feeding, suggesting that its supermassive black hole has undergone at least one latent period.
Another paper analyzed the light of a galaxy that had traveled more than 11 billion light-years, usually quite difficult to observe in detail at low frequencies.
This observation allowed us to investigate why these distant radio galaxies have specific signatures; ultimately, no conclusive answer could be found, but observation paves the way further in the future.
(R. Timmerman; LOFAR and Hubble Space Telescope)
And a probe on the spectacular radio galaxy Hercules A examined the ring structures in its radio lobes. These, the researchers concluded, were the result of intermittent strengthening and weakening of the jets, producing the observed structures.
These clues can help us understand the processes that produce and model radio rays, but the work collected has much deeper implications. The work also represents a significant milestone in radio astronomy, demonstrating the capabilities of a network like LOFAR to understand the mysteries of the Universe.
The series of works has been published in Astronomy and astrophysics.