Figure 1 .An image of the deep radio map covering the ELAIS-N1 region, with aligned galaxy jets. The image on the left has white...
 | |
Figure 1.An image of the deep radio map covering the
ELAIS-N1 region, with aligned galaxy jets.
The image on the
left has white circles around the aligned galaxies;
the
image on the right is without the circles. Credit: Prof. Russ Taylor |
Deep radio imaging by researchers in the
University of Cape Town and University of the Western Cape, in South Africa,
has revealed that supermassive black holes in a region of the distant universe
are all spinning out radio jets in the same direction – most likely a result
of primordial mass fluctuations in the early universe. The astronomers publish
their results in a new paper in Monthly Notices of the Royal Astronomical
Society.
The new result is the discovery – for the first time – of an alignment of
the jets of galaxies over a large volume of space, a finding made possible by a
three-year deep radio imaging survey of the radio waves coming from a region
called ELAIS-N1 using the Giant Metrewave Radio Telescope (GMRT).
The 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 Inter-University Institute for Data Intensive Astronomy, and
principal author of the Monthly Notices 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.
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 galaxies lined up.
The finding wasn't planned for: the initial
investigation was to explore the faintest radio sources in the universe, using
the best available telescopes –
a first view into the kind of universe that will be revealed by the South
African MeerKAT radio 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 uniformity (so-called isotropy) in the orientations of
galaxies. But these sensitive radio images offer a first opportunity to use
jets to reveal alignments of galaxies on physical scales of up to 100 Mpc. And
measurements from the total intensity radio emission of galaxy jets have the
advantage of not being affected by effects such as scattering, extinction and
Faraday Radiation, which may be an issue for other studies.
The presence of alignments and certain preferred
orientations can shed light on the orientation and evolution of the galaxies,
in relation to large-scale structures, and the motions in the primordial matter
fluctuations that gave rise to the structure of the Universe.
So what could these large-scale environmental
influences during galaxy formation or evolution have been? There are several
options: cosmic magnetic fields; fields associated with exotic particles
(axions); and cosmic strings are only some of the possible candidates that
could create an alignment in galaxies even on scales larger than galaxy
clusters.
The authors go on to note it would be
interesting to compare this with predictions of angular momentum structure from
universe simulations.
UWC Prof Romeel Dave, SARChI Chair in Cosmology
with Multi-Wavelength Data, who leads a team developing plans for universe
simulations that could explore the growth of large-scale structure from a
theoretical perspective, agrees: "This is not obviously expected based on
our current understanding of cosmology. It's a bizarre finding."
It's a mystery, and it's going to take a while
for technology and theory alike to catch up.
Such projects are already in the planning
stages; the SKA for example, 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 and as far back as we can go –
it's going to be an exciting time to be an astronomer."
A large-scale spin distribution has never been
predicted by theories – and an unknown phenomenon like this presents 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 cosmos works.
"We're beginning to understand how the
large-scale 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."
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