Media Release

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Astronomy: Unlocking the secrets of the
brightest galaxies (N&V) *IMAGES AND
VIDEO*
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NATURE
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Astronomy and planetary science
Embargo
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London: Wednesday 23 September 2015 18:00 (BST)
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New York: Wednesday 23 September 2015 13:00 (EDT)
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Tokyo: Thursday 24 September 2015 02:00 (JST)
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Sydney: Thursday 24 September 2015 03:00 (AEST)
A model for the formation of some of the most luminous galaxies in the Universe is reported in
this week’s Nature. These galaxies, known as submillimetre galaxies (SMGs), form stars at a
rate that is 1,000 times greater than that of the Milky Way, but their origin has remained
uncertain.
The extreme properties of SMGs have presented a challenge to existing models of galaxy
formation. Two general theories have been proposed: one suggests that collisions between two
galaxies may have driven a short-lived but spectacular burst of star formation; the other argues
that SMGs are long-lived objects that slowly accrete mass. However, neither scenario has been
able to fully reproduce the observed physical properties of SMGs.
Desika Narayanan and colleagues present galaxy-formation simulations that are able to form
SMGs that are consistent with the observed properties of these galaxies. The results indicate
that SMGs are not transient events but natural, long-lasting phases in the evolution of massive
galaxies, sustaining star formation rates of 500–1,000 solar masses per year for a billion years.
These intense star-formation rates seem to be fuelled in part by an ample gas reservoir enabled
by prior stellar feedback, rather than through major mergers, the authors suggest.
Writing in an accompanying News & Views article, Romeel Davé concludes that the authors
“have presented the first impressively viable model of SMG formation, allowing us a tantalizing
glimpse behind the mask of these behemoths of deep space.”
Article and author details
1. The formation of submillimetre-bright galaxies from gas infall
over a billion years
Corresponding Author
Desika Narayanan
Haverford College, Haverford, Pennsylvania, United States
Email: [email protected], Tel: +1 352 219 4301
N&V author
Romeel Davé
University of the Western Cape, Cape Town, South Africa
Email: [email protected]
DOI
10.1038/nature15383
Online paper*
http://nature.com/articles/doi:10.1038/nature15383
* Please link to the article in online versions of your report (the URL will go live after the embargo ends).
Geographical listings of authors
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Germany
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, South Africa
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& United States
Image 1
Caption: Image shows the gas density distribution of one instance in time of the model starburst galaxy, spanning
approximately 650,000 light years across. Extreme star formation in the central galaxy is fueled by significant gas
inflows, rendering it extremely bright.
Credit: Desika Narayanan
Image 2
Caption: Image shows distribution of galaxies across the infrared luminous region, at a given instance in time.
The colours denote the gas density. The model suggests that extreme infrared-luminous regions observed by
submillimetre-wave telescopes are often comprised of groups of galaxies in the early Universe (just a few billion
years after the Big Bang) that will grow to be massive clusters of galaxies at the present day.
Credit: Robert Thompson (NCSA)
Video 1
Caption: Movie shows rotating view of extreme infrared-luminous starburst region in the early Universe, just a few
billion years after the Big Bang. The model suggests that extreme infrared-luminous regions observed by
submillimetre-wave telescopes are often comprised of groups of galaxies in the early Universe that will grow to
be massive clusters in the present day.
Credit: Robert Thompson (NCSA)
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