The Spiderweb, imaged by the Hubble Space Telescope – a central galaxy
(MRC 1138-262) surrounded by hundreds of other star-forming 'clumps'.
Credit: NASA, ESA, George Miley and Roderik Overzier (Leiden
Observatory). Hi-res
.jpg)
In blue, the carbon monoxide gas detected in and around the Spiderweb
Credit: B. Emonts et al (CSIRO/ATCA). Hi-Res
Antennas of CSIRO's Compact Array telescope
Photo: David Smyth . Hi-Res
The Spiderweb
Zooming into the Spiderweb,
as imaged by NASA/ESA's Hubble Space Telescope. Credit: Akira Fujii,
Digitized Sky Survey 2 and ESA/Hubble.
Download
(mp4). Transcript: Stars
and galaxies seen from far away then the camera zooms in closer to
focus on a conglomerate of star-forming 'clumps' or 'proto-galaxies'
that are in the process of coming together as a single massive galaxy.
A CSIRO radio telescope has detected the raw material for making the
first stars in galaxies that formed when the Universe was just three
billion years old — less than a quarter of its current age. This opens
the way to studying how these early galaxies make their first stars.
The telescope is CSIRO's Australia Telescope Compact Array telescope
near Narrabri, NSW. "It one of very few telescopes in the world that can
do such difficult work, because it is both extremely sensitive and can
receive radio waves of the right wavelengths," says CSIRO astronomer
Professor Ron Ekers.
The raw material for making stars is cold molecular hydrogen gas, H2. It can't be detected directly but its presence is revealed by a 'tracer' gas, carbon monoxide (CO), which emits radio waves.
In one project, astronomer Dr Bjorn Emonts (CSIRO Astronomy and Space
Science) and his colleagues used the Compact Array to study a massive,
distant conglomerate of star-forming 'clumps' or 'proto-galaxies' that
are in the process of coming together as a single massive galaxy. This
structure, called the Spiderweb, lies more than ten thousand million
light-years away [at a redshift of 2.16].
Dr Emonts' team found that the Spiderweb contains at least sixty thousand million [6 x 1010]
times the mass of the Sun in molecular hydrogen gas, spread over a
distance of almost a quarter of a million light-years. This must be the
fuel for the star-formation that has been seen across the Spiderweb.
"Indeed, it is enough to keep stars forming for at least another 40
million years," says Emonts.
In a second set of studies, Dr Manuel Aravena (European Southern Observatory) and colleagues measured CO, and therefore H2, in two very distant galaxies [at a redshift of 2.7].
The faint radio waves from these galaxies were amplified by the
gravitational fields of other galaxies — ones that lie between us and
the distant galaxies. This process, called gravitational lensing, "acts
like a magnifying lens and allows us to see even more distant objects
than the Spiderweb," says Dr Aravena.
Dr Aravena's team was able to measure the amount of H2 in
both galaxies they studied. For one (called SPT-S 053816-5030.8), they
could also use the radio emission to make an estimate of how rapidly the
galaxy is forming stars — an estimate independent of the other ways
astronomers measure this rate.
The Compact Array's ability to detect CO is due to an upgrade that
has boosted its bandwidth — the amount of radio spectrum it can see at
any one time — sixteen-fold [from 256 MHz to 4 GHz], and made it far
more sensitive.
"The Compact Array complements the new ALMA telescope in Chile, which
looks for the higher-frequency transitions of CO," says Ron Ekers.
Read more media releases in our Media section.
Publications
Emonts BHC and 15 co-authors. CO(1-0) detection of molecular gas in
the massive Spiderweb Galaxy (z=2). Monthly Notices of the Royal
Astronomical Society 430, 3465 (2013). Online at
http://arxiv.org/abs/1301.6012
Aravena M and 28 co-authors. Large gas reservoirs and free-free
emission in two lensed star-forming galaxies at z = 2.7. Accepted for
publication in Monthly Notices of the Royal Astronomical Society. Online
at http://arxiv.org/abs/1305.0614.
More information
Professor Ron Ekers, CSIRO Astronomy and Space Science [in Sydney, Australia]
Mob: +61 419 146 313
Mob: +61 419 146 313
Mob: +34 692 744 507
Dr Manuel Aravena, European Southern Observatory [in Santiago, Chile]
maravena@eso.org
Office: +56 22 463 3256
maravena@eso.org
Office: +56 22 463 3256
Contact Information
Ms Helen Sim
Media and Public RelationsAstronomy and Space Science
Phone: +61 2 9372 4251
Alt Phone: +61 419 635 905
Email: Helen.Sim@csiro.au
Dr Ron Ekers
