Bright halos around distant quasars
Videos
3D animation of quasar halo
An international team of astronomers has
discovered glowing gas clouds surrounding distant quasars. This new
survey by the MUSE instrument on ESO’s Very Large Telescope indicates
that halos around quasars are far more common than expected. The
properties of the halos in this surprising find are also in striking
disagreement with currently accepted theories of galaxy formation in the
early Universe.
An international collaboration of astronomers, led by a group at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, has used the unrivalled observing power of MUSE on the Very Large Telescope
(VLT) at ESO’s Paranal Observatory to study gas around distant active
galaxies, less than two billion years after the Big Bang. These active
galaxies, called quasars, contain supermassive black holes
in their centres, which consume stars, gas, and other material at an
extremely high rate. This, in turn, causes the galaxy centre to emit
huge amounts of radiation, making quasars the most luminous and active
objects in the Universe.
The study involved 19 quasars, selected from among the
brightest that are observable with MUSE. Previous studies have shown
that around 10% of all quasars examined were surrounded by halos, made
from gas known as the intergalactic medium.
These halos extend up to 300 000 light-years away from the centres of
the quasars. This new study, however, has thrown up a surprise, with the
detection of large halos around all 19 quasars observed — far more
than the two halos that were expected statistically. The team suspects
this is due to the vast increase in the observing power of MUSE over
previous similar instruments, but further observations are needed to
determine whether this is the case.
“It is still too early to say if this is due to our new
observational technique or if there is something peculiar about the
quasars in our sample. So there is still a lot to learn; we are just at
the beginning of a new era of discoveries”, says lead author Elena Borisova, from the ETH Zurich.
The original goal of the study was to analyse the gaseous
components of the Universe on the largest scales; a structure sometimes
referred to as the cosmic web, in which quasars form bright nodes [1].
The gaseous components of this web are normally extremely difficult to
detect, so the illuminated halos of gas surrounding the quasars deliver
an almost unique opportunity to study the gas within this large-scale
cosmic structure.
The 19 newly-detected halos also revealed another surprise:
they consist of relatively cold intergalactic gas — approximately 10
000 degrees Celsius. This revelation is in strong disagreement with
currently accepted models of the structure and formation of galaxies,
which suggest that gas in such close proximity to galaxies should have
temperatures upwards of a million degrees.
The discovery shows the potential of MUSE for observing this type of object [2]. Co-author Sebastiano Cantalupo is very excited about the new instrument and the opportunities it provides: “We
have exploited the unique capabilities of MUSE in this study, which
will pave the way for future surveys. Combined with a new generation of
theoretical and numerical models, this approach will continue to provide
a new window on cosmic structure formation and galaxy evolution.”
Notes
[1] The cosmic web is the structure of the Universe at the largest scale. It is comprised of spindly filaments of primordial material (mostly hydrogen and helium gas) and dark matter
which connect galaxies and span the chasms between them. The material
in this web can feed along the filaments into galaxies and drive their
growth and evolution.
[2] MUSE
is an integral field spectrograph and combines spectrographic and
imaging capabilities. It can observe large astronomical objects in their
entirety in one go, and for each pixel measure the intensity of the
light as a function of its colour, or wavelength.
More Information
This research was presented in the paper "Ubiquitous giant
Lyα nebulae around the brightest quasars at z ~ 3.5 revealed with MUSE",
to appear in the Astrophysical Journal.
The team is composed of Elena Borisova, Sebastiano
Cantalupo, Simon J. Lilly, Raffaella A. Marino and Sofia G. Gallego
(Institute for Astronomy, ETH Zurich, Switzerland), Roland Bacon and
Jeremy Blaizot (University of Lyon, Centre de Recherche Astrophysique de
Lyon, Saint-Genis-Laval, France), Nicolas Bouché (Institut de Recherche
en Astrophysique et Planétologie, Toulouse, France), Jarle Brinchmann
(Leiden Observatory, Leiden, The Netherlands; Instituto de Astrofísica e
Ciências do Espaço, Porto, Portugal), C Marcella Carollo (Institute for
Astronomy, ETH Zurich, Switzerland), Joseph Caruana (Department of
Physics, University of Malta, Msida, Malta; Institute of Space Sciences
& Astronomy, University of Malta, Malta), Hayley Finley (Institut de
Recherche en Astrophysique et Planétologie, Toulouse, France), Edmund
C. Herenz (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany),
Johan Richard (Univ Lyon, Centre de Recherche Astrophysique de Lyon,
Saint-Genis-Laval, France), Joop Schaye and Lorrie A. Straka (Leiden
Observatory, Leiden, The Netherlands), Monica L. Turner (MIT-Kavli
Center for Astrophysics and Space Research, Massachusetts Institute of
Technology, Cambridge, Massachusetts, USA), Tanya Urrutia
(Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Anne
Verhamme (University of Lyon, Centre de Recherche Astrophysique de Lyon,
Saint-Genis-Laval, France), Lutz Wisotzki (Leibniz-Institut für
Astrophysik Potsdam, Potsdam, Germany).
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 16 countries: Austria, Belgium,
Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the
United Kingdom, along with the host state of Chile. 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 a major partner in ALMA, the largest astronomical
project in existence. And on Cerro Armazones, close to Paranal, ESO is
building the 39-metre European Extremely Large Telescope, the E-ELT,
which will become “the world’s biggest eye on the sky”.
Links
Contacts
Elena Borisova
ETH Zurich
Switzerland
Tel: +41 44 633 77 09
Email: borisova@phys.ethz.ch
Sebastiano Cantalupo
ETH Zurich
Switzerland
Tel: +41 44 633 70 57
Email: cantalupo@phys.ethz.ch
Mathias Jäger
Public Information Officer
Garching bei München, Germany
Tel: +49 176 62397500
Email: mjaeger@partner.eso.org
Source: ESO
