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Merging galaxies in the distant Universe through a gravitational magnifying glass
How gravitational lensing acts like a magnifying glass
Wide-field view of the sky around the gravitationally lensed galaxy merger H-ATLAS J142935.3-002836
Merging galaxies in the distant Universe through a gravitational magnifying glass
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ALMA applies methods of Sherlock Holmes
Using the Atacama Large
Millimeter/submillimeter Array (ALMA), and many other telescopes on the
ground and in space, an international team of astronomers has obtained
the best view yet of a collision that took place between two galaxies
when the Universe was only half its current age. They enlisted the help
of a galaxy-sized magnifying glass to reveal otherwise invisible detail.
These new studies of the galaxy H-ATLAS J142935.3-002836 have shown
that this complex and distant object looks like the well-known local
galaxy collision, the Antennae Galaxies.
The famous fictional detective Sherlock Holmes
used a magnifying lens to reveal barely visible but important evidence.
Astronomers are now combining the power of many telescopes on Earth and
in space [1] with a vastly larger form of cosmic lens to study a case of vigorous star formation in the early Universe.
“While astronomers are often limited by the power of their
telescopes, in some cases our ability to see detail is hugely boosted by
natural lenses, created by the Universe,” explains lead author
Hugo Messias of the Universidad de Concepción (Chile) and the Centro de
Astronomia e Astrofísica da Universidade de Lisboa (Portugal). “Einstein
predicted in his theory of general relativity that, given enough mass,
light does not travel in a straight line but will be bent in a similar
way to light refracted by a normal lens.”
These cosmic lenses are created by massive structures like galaxies
and galaxy clusters, which deflect the light from objects behind them
due to their strong gravity — an effect, called gravitational lensing.
The magnifying properties of this effect allow astronomers to study
objects which would not be visible otherwise and to directly compare
local galaxies with much more remote ones, seen when the Universe was
significantly younger.
But for these gravitational lenses to work, the lensing galaxy, and the one far behind it, need to be very precisely aligned.
Probing this object was at the limit of what is possible, so the
international team of astronomers started an extensive follow-up
campaign using the most powerful telescopes — both on the ground as well
as in space — including the NASA/ESA Hubble Space Telescope, ALMA, the Keck Observatory, the Karl Jansky Very Large Array
(JVLA), and others. The different telescopes provided different views,
which could be combined to get the best insight yet into the nature of
this unusual object.
The Hubble and Keck images revealed a detailed
gravitationally-induced ring of light around the foreground galaxy.
These high resolution images also showed that the lensing galaxy is an
edge-on disc galaxy — similar to our galaxy, the Milky Way — which
obscures parts of the background light due to the large dust clouds it
contains.
But this obscuration is not a problem for ALMA and the JVLA, since
these two facilities observe the sky at longer wavelengths, which are
unaffected by dust. Using the combined data the team discovered that the
background system was actually an ongoing collision between two
galaxies. From this point on, ALMA and the JVLA started to play a key
role in further characterising this object.
In particular, ALMA traced carbon monoxide,
which allows detailed studies of star formation mechanisms in galaxies.
The ALMA observations also allowed the motion of the material in the
more distant object to be measured. This was essential to show that the
lensed object is indeed an ongoing galactic collision forming hundreds
of new stars each year, and that one of the colliding galaxies still
shows signs of rotation; an indication that it was a disc galaxy just
before this encounter.
The system of these two colliding galaxies resembles an object that is much closer to us: the Antennae Galaxies.
This is a spectacular collision between two galaxies, which are
believed to have had a disc structure in the past. While the Antennae
system is forming stars at a rate of only a few tens of the mass of our
Sun each year, H1429-0028 turns more than 400 times the mass of the Sun
of gas into new stars each year.
Rob Ivison, ESO’s Director of Science and a co-author of the new study, concludes: “ALMA
enabled us to solve this conundrum because it gives us information
about the velocity of the gas in the galaxies, which makes it possible
to disentangle the various components, revealing the classic signature
of a galaxy merger. This beautiful study catches a galaxy merger red handed as it triggers an extreme starburst.”
Notes
[1] Among the armada of instruments
that were used to provide evidence to help unravel the mysteries of this
case were no fewer than three ESO telescopes — ALMA, APEX and VISTA. The other telescopes and surveys that were brought to bear were: the NASA/ESA Hubble Space Telescope, the Gemini South telescope, the Keck-II telescope, the NASA Spitzer Space Telescope, the Jansky Very Large Array, CARMA, IRAM and SDSS and WISE.
More information
The Atacama Large Millimeter/submillimeter
Array (ALMA), an international astronomy facility, is a partnership of
Europe, North America and East Asia in cooperation with the Republic of
Chile. ALMA is funded in Europe by the European Southern Observatory
(ESO), in North America by the U.S. National Science Foundation (NSF) in
cooperation with the National Research Council of Canada (NRC) and the
National Science Council of Taiwan (NSC) and in East Asia by the
National Institutes of Natural Sciences (NINS) of Japan in cooperation
with the Academia Sinica (AS) in Taiwan. ALMA construction and
operations are led on behalf of Europe by ESO, on behalf of North
America by the National Radio Astronomy Observatory (NRAO), which is
managed by Associated Universities, Inc. (AUI) and on behalf of East
Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint
ALMA Observatory (JAO) provides the unified leadership and management
of the construction, commissioning and operation of ALMA.
This research was presented in a paper entitled “Herschel-ATLAS and
ALMA HATLAS J142935.3-002836, a lensed major merger at redshift 1.027”,
by Hugo Messias et al., to appear online on 26 August 2014 in the
journal Astronomy & Astrophysics.
The team is composed of Hugo Messias (Universidad de Concepción,
Barrio Universitario, Chile; Centro de Astronomia e Astrofísica da
Universidade de Lisboa, Portugal), Simon Dye (School of Physics and
Astronomy, University of Nottingham, UK), Neil Nagar (Universidad de
Concepción, Barrio Universitario, Chile), Gustavo Orellana (Universidad
de Concepción, Barrio Universitario, Chile), R. Shane Bussmann
(Harvard-Smithsonian Center for Astrophysics, USA), Jae Calanog
(Department of Physics & Astronomy, University of California, USA),
Helmut Dannerbauer (Universität Wien, Institut für Astrophysik,
Austria), Hai Fu (Astronomy Department, California Institute of
Technology, USA), Edo Ibar (Pontificia Universidad Católica de Chile,
Departamento de Astronomía y Astrofísica, Chile), Andrew Inohara
(Department of Physics & Astronomy, University of California, USA),
R. J. Ivison (Institute for Astronomy, University of Edinburgh, Royal
Observatory, UK; ESO, Garching, Germany), Mattia Negrello (INAF,
Osservatorio Astronomico di Padova, Italy), Dominik A. Riechers
(Astronomy Department, California Institute of Technology, USA;
Department of Astronomy, Cornell University, USA), Yun-Kyeong Sheen
(Universidad de Concepción, Barrio Universitario, Chile), Simon Amber
(The Open University, Milton Keynes, UK), Mark Birkinshaw (H. H. Wills
Physics Laboratory, University of Bristol, UK; Harvard-Smithsonian
Center for Astrophysics, USA), Nathan Bourne (School of Physics and
Astronomy, University of Nottingham, UK), Dave L. Clements (Astrophysics
Group, Imperial College London, UK), Asantha Cooray (Department of
Physics & Astronomy, University of California, USA; Astronomy
Department, California Institute of Technology, USA), Gianfranco De
Zotti (INAF, Osservatorio Astronomico di Padova, Italy), Ricardo Demarco
(Universidad de Concepción, Barrio Universitario, Chile), Loretta Dunne
(Department of Physics and Astronomy, University of Canterbury, New
Zealand; Institute for Astronomy, University of Edinburgh, Royal
Observatory, UK), Stephen Eales (School of Physics and Astronomy,
Cardiff University,UK), Simone Fleuren (School of Mathematical Sciences,
University of London, UK), Roxana E. Lupu (Department of Physics and
Astronomy, University of Pennsylvania, USA), Steve J. Maddox (Department
of Physics and Astronomy, University of Canterbury, New Zealand;
Institute for Astronomy, University of Edinburgh, Royal Observatory,
UK), Michał J. Michałowski (Institute for Astronomy, University of
Edinburgh, Royal Observatory, UK), Alain Omont (Institut d’Astrophysique
de Paris, UPMC Univ. Paris, France), Kate Rowlands (School of Physics
& Astronomy, University of St Andrews, UK), Dan Smith (Centre for
Astrophysics Research, Science & Technology Research Institute,
University of Hertfordshire, UK), Matt Smith (School of Physics and
Astronomy, Cardiff University,UK) and Elisabetta Valiante (School of
Physics and Astronomy, Cardiff University, UK).
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
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Contacts
Hugo Messias
Universidad de Concepción, Chile / Centro de Astronomia e Astrofísica da Universidade de Lisboa, Portugal
Tel: +351 21 361 67 47/30
Email: hmessias@oal.ul.pt
Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO
