Simulation of large scale structure
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VLT reveals alignments between supermassive black hole axes and large-scale structure
New observations with ESO’s Very Large
Telescope (VLT) in Chile have revealed alignments over the largest
structures ever discovered in the Universe. A European research team has
found that the rotation axes of the central supermassive black holes in
a sample of quasars are parallel to each other over distances of
billions of light-years. The team has also found that the rotation axes
of these quasars tend to be aligned with the vast structures in the
cosmic web in which they reside.
Quasars are
galaxies with very active supermassive black holes at their centres.
These black holes are surrounded by spinning discs of extremely hot
material that is often spewed out in long jets along their axes of
rotation. Quasars can shine more brightly than all the stars in the rest
of their host galaxies put together.
A team led by Damien Hutsemékers from the University of Liège in Belgium used the FORS instrument on the VLT
to study 93 quasars that were known to form huge groupings spread over
billions of light-years, seen at a time when the Universe was about one
third of its current age.
“The first odd thing we noticed was that some of the quasars’
rotation axes were aligned with each other — despite the fact that these
quasars are separated by billions of light-years,” said Hutsemékers.
The team then went further and looked to see if the rotation axes
were linked, not just to each other, but also to the structure of the
Universe on large scales at that time.
When astronomers look at the distribution of galaxies on scales of
billions of light-years they find that they are not evenly distributed.
They form a cosmic web of filaments and clumps around huge voids where
galaxies are scarce. This intriguing and beautiful arrangement of
material is known as large-scale structure.
The new VLT results indicate that the rotation axes of the quasars
tend to be parallel to the large-scale structures in which they find
themselves. So, if the quasars are in a long filament then the spins of
the central black holes will point along the filament. The researchers
estimate that the probability that these alignments are simply the
result of chance is less than 1%.
“A correlation between the orientation of quasars and the
structure they belong to is an important prediction of numerical models
of evolution of our Universe. Our data provide the first observational
confirmation of this effect, on scales much larger that what had been
observed to date for normal galaxies,” adds Dominique Sluse of the Argelander-Institut für Astronomie in Bonn, Germany and University of Liège.
The team could not see the rotation axes or the jets of the quasars directly. Instead they measured the polarisation
of the light from each quasar and, for 19 of them, found a
significantly polarised signal. The direction of this polarisation,
combined with other information, could be used to deduce the angle of
the accretion disc and hence the direction of the spin axis of the
quasar.
“The alignments in the new data, on scales even bigger than
current predictions from simulations, may be a hint that there is a
missing ingredient in our current models of the cosmos,” concludes Dominique Sluse.
More Information
This research was presented in a paper
entitled “Alignment of quasar polarizations with large-scale
structures“, by D. Hutsemékers et al., to appear in the journal Astronomy & Astrophysics on 19 November 2014.
The team is composed of D. Hutsemékers (Institut d’Astrophysique et
de Géophysique, Université de Liège, Liège, Belgium), L. Braibant
(Liège), V. Pelgrims (Liège) and D. Sluse (Argelander-Institut für
Astronomie, Bonn, Germany; Liège).
ESO is the foremost intergovernmental astronomy organisation in
Europe and the world’s most productive ground-based astronomical
observatory by far. It is supported by 15 countries: Austria, Belgium,
Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Portugal, Spain, Sweden, Switzerland and the United
Kingdom. ESO carries out an ambitious programme focused on the design,
construction and operation of powerful ground-based observing facilities
enabling astronomers to make important scientific discoveries. ESO also
plays a leading role in promoting and organising cooperation in
astronomical research. ESO operates three unique world-class observing
sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO
operates the Very Large Telescope, the world’s most advanced
visible-light astronomical observatory and two survey telescopes. VISTA
works in the infrared and is the world’s largest survey telescope and
the VLT Survey Telescope is the largest telescope designed to
exclusively survey the skies in visible light. ESO is the European
partner of a revolutionary astronomical telescope ALMA, the largest
astronomical project in existence. ESO is currently planning the
39-metre European Extremely Large optical/near-infrared Telescope, the
E-ELT, which will become “the world’s biggest eye on the sky”.
Links
Contacts:
Damien Hutsemékers
Institut d’Astrophysique et de Géophysique — Université de Liège
Liège, Belgium
Tel: +32 4 366 9760
Email: hutsemekers@astro.ulg.ac.be
Dominique Sluse
Institut d'Astrophysique et de Géophysique — Université de Liège
Liège, Belgium
Tel: +32 4 366 9797
Email: dsluse@ulg.ac.be
Richard Hook
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO
