One direction, cosmically speaking: Astronomers in South Africa discover mysterious alignment of black holes
Deep radio imaging by researchers in the University of Cape Town and the University of the Western Cape has revealed that supermassive black holes in 64 galaxies are all spinning out radio jets in the same direction – most likely a result of primordial mass fluctuations in the early universe, a new paper in MNRAS reports today.
The new result is the discovery – for the first time – of an alignment of the jets of radio galaxies over a large volume of space, a finding made possible by a three-year deep radio imaging survey of radio waves coming from a region called ELAIS-N1 region using the Giant Metrewave Radio Telescope (GMRT).
The radio jets are produced by the supermassive black holes at the centres of these galaxies, and the only way for this alignment to exist is if supermassive black holes are all spinning in the same direction, says Prof Andrew Russ Taylor, joint UWC/UCT SKA Chair, Director of the recently-launched Institute for Data Intensive Astronomy and principal author of the study.
“Since these black holes don’t know about each other, or have any way of exchanging information or influencing each other directly over such vast scales, this spin alignment must have occurred during the formation of the galaxies in the early universe,” he notes.
This implies that there is a coherent spin in the structure of this volume of space that was formed from the primordial mass fluctuations that seeded the creation of the large scale structure of the universe.
(Astronomical) Image is Everything
With study co-author – and UCT PhD student currently working at the National Radio Astronomy Observatory, Socorro, New Mexico, USA – Preshanth Jagannathan, the team discovered the alignment after the initial image had been made. Within the large-scale structure, there were regions where the spin axes of all 64 galaxies lined up.
The finding wasn’t planned for: the initial investigation was just to explore the faintest radio sources in the universe, using the best available telescopes – a first view into view into the kind of universe that will be revealed by the South African MeerKAT telescope and the Square Kilometre Array (SKA), the world’s most powerful radio telescope and one of the biggest scientific instruments ever devised.
Earlier observational studies had previously detected deviations from isotropy in the orientation of galaxies. But these sensitive radio images offer a first opportunity to use radio jets to reveal alignments of radio galaxies on physical scales of up to 100 Megaparsecs (Mpc). And measurements from the total intensity radio emission of jets from active galactic nuclei have the advantage of not being affected by propagation effects such as scattering, extinction and Faraday Radiation, which may be an issue for optical and polarimetric studies. The presence of alignments and certain preferred orientations can shed light on the orientation and evolution of the galaxies, relation to large scale structures and the motions in the primordial matter fluctuations that gave rise to the structure of the Universe.
It would be interesting to compare this implication with predictions of angular momentum structure from universe simulations, the study authors note.
UWC Prof Romeel Dave, SARChI Chair in Cosmology with Multi-Wavelength Data, who leads a team developing plans for universe simulations that could explore this phenomenon from a theoretical perspective of the growth of large scale structure, agrees: “It’s a bizarre finding. This is not obviously expected based on our current understanding of cosmology.”
So what could these large-scale environmental influences during galaxy formation or evolution have been? There are several options: cosmic magnetic fields; axionic fields post-inflation; and cosmic strings are only some of the possible candidates that could effect an alignment in galaxies even on scales larger than galaxy clusters.
It’s a mystery, and it’s going to take a while for technology and theory alike to catch up.
Such imaging projects are in the planning stages for the SKA and its precursor telescopes, the South African MeerKAT array and the Australian SKA Pathfinder (ASKAP).
“GMRT is one of the largest and most sensitive radio telescope arrays in the world,” notes Prof Taylor, “but we really need MeerKAT to make the very sensitive maps, over a very large area and with great detail, that will be necessary to differentiate between possible explanations. It opens up a whole new research area for these instruments, which will probe as deeply into the universe and as far back as we can go – it’s going to be an exciting time to be an astronomer.”
So what does this all mean? Well, as you may have heard, it’s a mystery – and that always means something.
A large-scale spin distribution has never been predicted by theories – and where there’s an unknown phenomenon like this, there’s a challenge that theories about the origins of the universe need to account for, and an opportunity to find out more about the way the universe works.
“We’re beginning to understand how the large structure of the universe came about, starting from the Big Bang and growing as a result of disturbances in the early universe, to what we have today,” says Prof Taylor, “and that helps us explore what the universe of tomorrow will be like.”