Monstrous Star-Forming Regions Seen in Ancient Galaxy
After poring over the details of the most perfect Einstein Ring imaged to date, ALMA astronomers have discovered that this distant galaxy is a frenzy of star formation.
When the Atacama Large Millimeter/submillimeter Array (ALMA) first imaged this near-perfect Einstein Ring in the depths of space, the detail and geometry of this beautiful quirk in spacetime captivated the world.
Now that astronomers have had time to pore over the data recorded by the huge observatory, located in the Chilean Atacama Desert, some intriguing details have begun to emerge from the warped galaxy called SDP.81, chiefly that it contains some of the most distant and massive star formation regions ever seen. This galaxy was forming in the first billion years after the Big Bang.
ANALYSIS: ALMA Captures Ancient Galaxy's Near-Perfect Einstein Ring
"The reconstructed ALMA image of the galaxy is spectacular," said Rob Ivison, ESO's Director for Science and co-author on two recent papers based on SDP.81. "ALMA's huge collecting area, the large separation of its antennas, and the stable atmosphere above the Atacama desert all lead to exquisite detail in both images and spectra. That means that we get very sensitive observations, as well as information about how the different parts of the galaxy are moving. We can study galaxies at the other end of the Universe as they merge and create huge numbers of stars. This is the kind of stuff that gets me up in the morning!"
Gravitational lensing occurs when a massive object, like a black hole, galaxy or even cluster of galaxies pass in front of a more distant galaxy. The foreground mass can act as a natural "lens" in spacetime, magnifying the starlight from the more distant galaxy.
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This occurs because the lens' mass will create a curvature of the spacetime surrounding it, thereby deflecting the light from the more distant galaxy. This cosmic effect has been put to great use by the Hubble Space Telescope for example, where the "Frontier Fields" project looks out for gravitationally-lensed galaxies in the hope of super-boosting Hubble's magnifying power.
Often, lensed galaxies appear as arcs, but sometimes, if the alignment is near-perfect, the distant galaxy can form an Einstein Ring, named after Albert Einstein who formulated the equations of general relativity 100 years ago. Gravitational lenses are cosmic proof of Einstein's theories, showing that spacetime warps around massive objects as the physicist predicted.
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After taking detailed observations of this particular Einstein Ring, the most detailed to date, and using sophisticated software to reconstruct the light from SDP.81, astronomers have discovered that this galaxy is erupting with huge star-forming nebulae, not so dissimilar to the Orion Nebula that is known to be birthing stars in our galaxy, only many times bigger.
By "de-warping" this ALMA observation, astronomers have worked out that these clumps of star formation are around 200 light-years wide, brimming with star-birth thousands of times more active than any region in our own galaxy.
The left image shows the sharp ALMA image of the Einstein ring, with the foreground lensing galaxy being invisible to ALMA. The resulting reconstructed image of the distant galaxy (right) using sophisticated models of the magnifying gravitational lens, reveal fine structures within the ring that have never been seen before: Several dust clouds within the galaxy, which are thought to be giant cold molecular clouds, the birthplaces of stars and planets.
The Atacama Large Millimeter/submillimeter Array (ALMA) is finally complete, after the project's final 12-meter antenna was handed over on Sept. 30, 2013. The 66th dish, shown here, is the last of 25 European-built instruments. The Joint ALMA Observatory (JAO) is a collaboration between the European Southern Observatory (ESO), the National Radio Astronomy Observatory (NRAO) and the National Astronomical Observatory of Japan (NAOJ).
All 66 millimetre/submillimetre-wave radio antennas are expected to be operational by the end of 2013, working together as one large telescope. ALMA will operate as an interferometer, spread over 16 kilometers of the Chajnantor Plateau in the Atacama Desert, Chile.
ALMA is sensitive to millimetre and submillimetre wavelengths, between infrared light and radio waves in the electromagnetic spectrum, a range that will help astronomers peel back the veil on distant objects in the Cosmos.
The giant antenna transporter, called Otto, delivers the final antenna to the array on Sept. 30, 2013.
The final dish was built by the European AEM Consortium, the largest of the project's contracts. North America delivered 25 12-meter antennas and East Asia delivered 16 (four 12-meter and twelve 7-meter).
"This is an important milestone for the ALMA Observatory since it enables astronomers in Europe and elsewhere to use the complete ALMA telescope, with its full sensitivity and collecting area," said Wolfgang Wild, the European ALMA Project Manager.
An artist's impression of the complete ALMA array in the Atacama Desert.
Possibly breaking the record for altitude record for a radio controlled hexacopter, this aerial photograph of ALMA in the extreme environment of the Atacama Desert in Chile was taken earlier this year.