Massive galaxies discovered in the early Universe
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Massive galaxies discovered in the early Universe
VISTA pinpoints earliest giant galaxies
ESO’s VISTA survey telescope has spied a
horde of previously hidden massive galaxies that existed when the
Universe was in its infancy. By discovering and studying more of these
galaxies than ever before, astronomers have, for the first time, found
out exactly when such monster galaxies first appeared.
Just counting the number of galaxies in a patch of sky provides a way
to test astronomers’ theories of galaxy formation and evolution.
However, such a simple task becomes increasingly hard as astronomers
attempt to count the more distant and fainter galaxies. It is further
complicated by the fact that the brightest and easiest galaxies to
observe — the most massive galaxies in the Universe — are rarer the
further astronomers peer into the Universe’s past, whilst the more
numerous less bright galaxies are even more difficult to find.
A team of astronomers, led by Karina Caputi of the Kapteyn Astronomical Institute
at the University of Groningen, has now unearthed many distant galaxies
that had escaped earlier scrutiny. They used images from the UltraVISTA survey, one of six projects using VISTA
to survey the sky at near-infrared wavelengths, and made a census of
faint galaxies when the age of the Universe was between just 0.75 and
2.1 billion years old.
UltraVISTA has been imaging the same patch of sky, nearly four times
the size of a full Moon, since December 2009. This is the largest patch
of sky ever imaged to these depths at infrared wavelengths. The team
combined these UltraVISTA observations with those from the NASA Spitzer Space Telescope, which probes the cosmos at even longer, mid-infrared wavelengths [1].
“We uncovered 574 new massive galaxies — the largest sample of such hidden galaxies in the early Universe ever assembled,” explains Karina Caputi. “Studying them allows us to answer a simple but important question: when did the first massive galaxies appear?”
Imaging the cosmos at near-infrared wavelengths allowed the astronomers to see objects that are both obscured by dust, and extremely distant [2], created when the Universe was just an infant.
The team discovered an explosion in the numbers of these galaxies in a
very short amount of time. A large fraction of the massive galaxies [3] we now see around us in the nearby Universe were already formed just three billion years after the Big Bang.
“
We found no evidence of these massive galaxies earlier than
around one billion years after the Big Bang, so we’re confident that
this is when the first massive galaxies must have formed,” concludes
Henry Joy McCracken, a co-author on the paper [4].
In addition, the astronomers found that massive galaxies were more
plentiful than had been thought. Galaxies that were previously hidden
make up half of the total number of massive galaxies present when the
Universe was between 1.1 and 1.5 billion years old [5].
These new results, however, contradict current models of how galaxies
evolved in the early Universe, which do not predict any monster galaxies
at these early times.
To complicate things further, if massive galaxies are unexpectedly dustier in the early Universe than astronomers predict then even UltraVISTA wouldn’t be able to detect them. If this is indeed the case, the currently-held picture of how galaxies formed in the early Universe may also require a complete overhaul.
The Atacama Large Millimeter/submillimeter Array (ALMA)
will also search for these game-changing dusty galaxies. If they are
found they will also serve as targets for ESO’s 39-metre European
Extremely Large Telescope (E-ELT), which will enable detailed observations of some of the first ever galaxies.
Notes
[1] ESO’s VISTA telescope observed in the near-infrared wavelength range 0.88–2.15 μm while Spitzer performed observations in the mid-infrared at 3.6 and 4.5 μm.
[2] The expansion of space means that the more distant a galaxy is, the faster it appears to be speeding away from an observer on Earth. This stretching causes the light from these distant objects to be shifted into redder parts of the spectrum, meaning that observations in the near-to-mid infrared are necessary to capture the light from these galaxies.
[3] In this context, "massive" means more than 50 billion times the mass of the Sun. The total mass of the stars in the Milky Way is also close to this figure.
[4] The team found no evidence of massive galaxies beyond a redshift of 6, equivalent to times less than 0.9 billion years after the Big Bang.
[5] This is equivalent to redshifts between z=5 and z=4.
More Information
Contacts
Karina I. Caputi
Kapteyn Astronomical Institute – University of Groningen
The Netherlands
Email: karina@astro.rug.nl
Henry J. McCracken
Institut d'Astrophysique de Paris
France
Email: hjmcc@iap.fr
Bo Milvang-Jensen
Dark Cosmology Center – University of Copenhagen
Denmark
Email: milvang@dark-cosmology.dk
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Notes
[1] ESO’s VISTA telescope observed in the near-infrared wavelength range 0.88–2.15 μm while Spitzer performed observations in the mid-infrared at 3.6 and 4.5 μm.
[2] The expansion of space means that the more distant a galaxy is, the faster it appears to be speeding away from an observer on Earth. This stretching causes the light from these distant objects to be shifted into redder parts of the spectrum, meaning that observations in the near-to-mid infrared are necessary to capture the light from these galaxies.
[3] In this context, "massive" means more than 50 billion times the mass of the Sun. The total mass of the stars in the Milky Way is also close to this figure.
[4] The team found no evidence of massive galaxies beyond a redshift of 6, equivalent to times less than 0.9 billion years after the Big Bang.
[5] This is equivalent to redshifts between z=5 and z=4.
More Information
This research was presented in a paper entitled “Spitzer Bright,
UltraVISTA Faint Sources in COSMOS: The Contribution to the Overall
Population of Massive Galaxies at z = 3-7”, by K. Caputi et al., which
appeared in the Astrophysical Journal.
The team is composed of Karina I. Caputi (Kapteyn
Astronomical Institute, University of Groningen, Netherlands), Olivier
Ilbert (Laboratoire d'Astrophysique de Marseille, Aix-Marseille
University, France), Clotilde Laigle (Institut d'Astrophysique de Paris,
France), Henry J. McCracken (Institut d'Astrophysique de Paris,
France), Olivier Le Fèvre (Laboratoire d'Astrophysique de Marseille,
Aix-Marseille University, France), Johan Fynbo (Dark Cosmology Centre,
Niels Bohr Institute, Copenhagen, Denmark), Bo Milvang-Jensen (Dark
Cosmology Centre), Peter Capak (NASA/JPL Spitzer Science Centre,
California Institute of Technology, Pasadena, California, USA), Mara
Salvato (Max-Planck Institute for Extragalactic Physics, Garching,
Germany) and Yoshiaki Taniguchi (Research Center for Space and Cosmic
Evolution, Ehime University, Japan).
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
Karina I. Caputi
Kapteyn Astronomical Institute – University of Groningen
The Netherlands
Email: karina@astro.rug.nl
Henry J. McCracken
Institut d'Astrophysique de Paris
France
Email: hjmcc@iap.fr
Bo Milvang-Jensen
Dark Cosmology Center – University of Copenhagen
Denmark
Email: milvang@dark-cosmology.dk
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
