Computer simulation of a Lyman-alpha Blob
Infographic explaining how a Lyman-alpha Blob functions
Giant space blob glows from within
Closing in on a giant space blob
Wide-field view of the sky around a giant space blob
Videos
Zooming in on a giant space blob
An international team using ALMA, along with ESO’s Very Large Telescope and other telescopes, has discovered the true nature of a rare object in the distant Universe called a Lyman-alpha Blob. Up to now astronomers did not understand what made these huge clouds of gas shine so brightly, but ALMA has now seen two galaxies at the heart of one of these objects and they are undergoing a frenzy of star formation that is lighting up their surroundings. These large galaxies are in turn at the centre of a swarm of smaller ones in what appears to be an early phase in the formation of a massive cluster of galaxies. The two ALMA sources are expected to evolve into a single giant elliptical galaxy.
Notes
[1] The negatively charged electrons that orbit the positively charged nucleus in an atom have quantised energy levels. That is, they can only exist in specific energy states, and they can only transition between them by gaining or losing precise amounts of energy. Lyman-alpha radiation is produced when electrons in hydrogen atoms drop from the second-lowest to the lowest energy level. The precise amount of energy lost is released as light with a particular wavelength, in the ultraviolet part of the spectrum, which astronomers can detect with space telescopes or on Earth in the case of redshifted objects. For LAB-1, at redshift of z~3, the Lyman-alpha light is seen as visible light.
[3] The instruments used were the Space Telescope Imaging Spectograph (STIS) on the NASA/ESA Hubble Space Telescope and the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) mounted on the Keck 1 telescope on Hawaii.
More Information
An international team using ALMA, along with ESO’s Very Large Telescope and other telescopes, has discovered the true nature of a rare object in the distant Universe called a Lyman-alpha Blob. Up to now astronomers did not understand what made these huge clouds of gas shine so brightly, but ALMA has now seen two galaxies at the heart of one of these objects and they are undergoing a frenzy of star formation that is lighting up their surroundings. These large galaxies are in turn at the centre of a swarm of smaller ones in what appears to be an early phase in the formation of a massive cluster of galaxies. The two ALMA sources are expected to evolve into a single giant elliptical galaxy.
Lyman-alpha Blobs
(LABs) are gigantic clouds of hydrogen gas that can span hundreds of
thousands of light-years and are found at very large cosmic distances.
The name reflects the characteristic wavelength of ultraviolet light
that they emit, known as Lyman-alpha radiation [1].
Since their discovery, the processes that give rise to LABs have been
an astronomical puzzle. But new observations with ALMA may now have now
cleared up the mystery.
One of the largest Lyman-alpha Blobs known, and the most
thoroughly studied, is SSA22-Lyman-alpha blob 1, or LAB-1. Embedded in
the core of a huge cluster of galaxies in the early stages of formation,
it was the very first such object to be discovered — in 2000 — and is
located so far away that its light has taken about 11.5 billion years to
reach us.
A team of astronomers, led by Jim Geach, from the Centre for Astrophysics Research of the University of Hertfordshire, UK, has now used the Atacama Large Millimeter/Submillimeter Array’s
(ALMA) unparallelled ability to observe light from cool dust clouds in
distant galaxies to peer deeply into LAB-1. This allowed them to
pinpoint and resolve several sources of submillimetre emission [2].
They then combined the ALMA images with observations from the Multi Unit Spectroscopic Explorer (MUSE) instrument mounted on ESO’s Very Large Telescope
(VLT), which map the Lyman-alpha light. This showed that the ALMA
sources are located in the very heart of the Lyman-alpha Blob, where
they are forming stars at a rate over 100 times that of the Milky Way.
Deep imaging with the NASA/ESA Hubble Space Telescope and spectroscopy at the W. M. Keck Observatory [3]
showed in addition that the ALMA sources are surrounded by numerous
faint companion galaxies that could be bombarding the central ALMA
sources with material, helping to drive their high star formation rates.
The team then turned to a sophisticated simulation of
galaxy formation to demonstrate that the giant glowing cloud of
Lyman-alpha emission can be explained if ultraviolet light produced by
star formation in the ALMA sources scatters off the surrounding hydrogen
gas. This would give rise to the Lyman-alpha Blob we see.
Jim Geach, lead author of the new study, explains: “Think
of a streetlight on a foggy night — you see the diffuse glow because
light is scattering off the tiny water droplets. A similar thing is
happening here, except the streetlight is an intensely star-forming
galaxy and the fog is a huge cloud of intergalactic gas. The galaxies
are illuminating their surroundings.”
Understanding how galaxies form and evolve is a massive
challenge. Astronomers think Lyman-alpha Blobs are important because
they seem to be the places where the most massive galaxies in the
Universe form. In particular, the extended Lyman-alpha glow provides
information on what is happening in the primordial gas clouds
surrounding young galaxies, a region that is very difficult to study,
but critical to understand.
Jim Geach concludes, “What’s exciting about these blobs
is that we are getting a rare glimpse of what’s happening around these
young, growing galaxies. For a long time the origin of the extended
Lyman-alpha light has been controversial. But with the combination of
new observations and cutting-edge simulations, we think we have solved a
15-year-old mystery: Lyman-alpha Blob-1 is the site of formation of a
massive elliptical galaxy that will one day be the heart of a giant
cluster. We are seeing a snapshot of the assembly of that galaxy 11.5
billion years ago.”
Notes
[1] The negatively charged electrons that orbit the positively charged nucleus in an atom have quantised energy levels. That is, they can only exist in specific energy states, and they can only transition between them by gaining or losing precise amounts of energy. Lyman-alpha radiation is produced when electrons in hydrogen atoms drop from the second-lowest to the lowest energy level. The precise amount of energy lost is released as light with a particular wavelength, in the ultraviolet part of the spectrum, which astronomers can detect with space telescopes or on Earth in the case of redshifted objects. For LAB-1, at redshift of z~3, the Lyman-alpha light is seen as visible light.
[2] Resolution is the
ability to see that objects are separated. At low resolution, several
bright sources at a distance would seem like a single glowing spot, and
only at closer quarters would each source be distinguishable. ALMA’s
high resolution has resolved what previously appeared to be a single
blob into two separate sources.
More Information
This research was presented in a paper entitled “ALMA
observations of Lyman-α Blob 1: Halo sub-structure illuminated from
within” by J. Geach et al., to appear in the Astrophysical Journal.
The team is composed of J. E. Geach (Centre for
Astrophysics Research, University of Hertfordshire, Hatfield, UK), D.
Narayanan (Department of Physics and Astronomy, Haverford College,
Haverford PA, USA; Department of Astronomy, University of Florida,
Gainesville FL, USA), Y. Matsuda (National Astronomical Observatory of
Japan, Mitaka, Tokyo, Japan; The Graduate University for Advanced
Studies, Mitaka, Tokyo, Japan), M. Hayes (Stockholm University,
Department of Astronomy and Oskar Klein Centre for Cosmoparticle
Physics, Stockholm, Sweden), Ll. Mas-Ribas (Institute of Theoretical
Astrophysics, University of Oslo, Oslo, Norway), M. Dijkstra (Institute
of Theoretical Astrophysics, University of Oslo, Oslo, Norway), C. C.
Steidel (California Institute of Technology, Pasadena CA, USA ), S. C.
Chapman (Department of Physics and Atmospheric Science, Dalhousie
University, Halifax, Canada ), R. Feldmann (Department of Astronomy,
University of California, Berkeley CA, USA ), A. Avison (UK ALMA
Regional Centre Node; Jodrell Bank Centre for Astrophysics, School of
Physics and Astronomy, The University of Manchester, Manchester, UK), O.
Agertz (Department of Physics, University of Surrey, Guildford, UK), Y.
Ao (National Astronomical Observatory of Japan, Mitaka, Tokyo, Japan),
M. Birkinshaw (H.H. Wills Physics Laboratory, University of Bristol,
Bristol, UK), M. N. Bremer (H.H. Wills Physics Laboratory, University of
Bristol, Bristol, UK), D. L. Clements (Astrophysics Group, Imperial
College London, Blackett Laboratory, London, UK), H. Dannerbauer
(Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain;
Universidad de La Laguna, Astrofísica, La Laguna, Tenerife, Spain), D.
Farrah (Department of Physics, Virginia Tech, Blacksburg VA, USA), C. M.
Harrison (Centre for Extragalactic Astronomy, Department of Physics,
Durham University, Durham, UK), M. Kubo (National Astronomical
Observatory of Japan, Mitaka, Tokyo, Japan), M. J. Michałowski
(Institute for Astronomy, University of Edinburgh, Royal Observatory,
Edinburgh, UK), D. Scott (Department of Physics & Astronomy,
University of British Columbia, Vancouver, Canada), M. Spaans (Kapteyn
Astronomical Institute, University of Groningen, Groningen, Netherlands)
, J. Simpson (Institute for Astronomy, University of Edinburgh, Royal
Observatory, Edinburgh, UK), A. M. Swinbank (Centre for Extragalactic
Astronomy, Department of Physics, Durham University, Durham, UK ), Y.
Taniguchi (The Open University of Japan, Chiba, Japan), E. van Kampen
(ESO, Garching, Germany), P. Van Der Werf (Leiden Observatory, Leiden
University, Leiden, The Netherlands), A. Verma (Oxford Astrophysics,
Department of Physics, University of Oxford, Oxford, UK) and T. Yamada
(Astronomical Institute, Tohoku University, Miyagi, Japan).
The Atacama Large Millimeter/submillimeter Array (ALMA), an
international astronomy facility, is a partnership of ESO, the US
National Science Foundation (NSF) and the National Institutes of Natural
Sciences (NINS) of Japan in cooperation with the Republic of Chile.
ALMA is funded by ESO on behalf of its Member States, by NSF in
cooperation with the National Research Council of Canada (NRC) and the
National Science Council of Taiwan (NSC) and by NINS in cooperation with
the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space
Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf
of its Member States; by the National Radio Astronomy Observatory
(NRAO), managed by Associated Universities, Inc. (AUI), on behalf of
North America; and by the National Astronomical Observatory of Japan
(NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides
the unified leadership and management of the construction,
commissioning and operation of ALMA.
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
Contact
Jim Geach
Centre for Astrophysics Research, University of Hertfordshire
Hatfield, UK
Email: j.geach@herts.ac.uk
Matthew Hayes
Stockholm University
Stockholm, Sweden
Tel: +46 (0)8 5537 8521
Stockholm University
Stockholm, Sweden
Tel: +46 (0)8 5537 8521
Email: matthew@astro.su.se
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO
