galaxy collision
August 27, 2014

ALMA, Hubble Help Astronomers Obtain Best Ever View Of Early Merging Galaxies

Chuck Bednar for - Your Universe Online

Using a battery of observatories that included the Atacama Large Millimeter/submillimeter Array (ALMA) and the Hubble Space Telescope, an international team of astronomers has obtained the best view to date of a collision between two galaxies that took place when the universe was just a fraction of its current age.

According to ESA, the team also utilized a gravitational lens to magnify galaxy HATLAS J142935.3-002836, revealing otherwise undetectable details and finding that this distant and complex object is similar in appearance to a local galaxy collision known as the Antennae Galaxies. Their work is detailed in the latest edition of the journal Astronomy & Astrophysics.

[ Watch the Video: Zooming In On A Gravitationally Lensed Galaxy Merger In The Distant Universe ]

“While astronomers are often limited by the power of their telescopes, in some cases our ability to see detail is hugely boosted by natural lenses created by the Universe,” lead author Hugo Messias of the Universidad de Concepción in Chile and the Centro de Astronomia e Astrofísica da Universidade de Lisboa in Portugal explained in a statement. “Einstein predicted in his theory of General Relativity that, given enough mass, light does not travel in a straight line but will be bent in a similar way to a normal lens.”

Massive structures such as galaxies and galaxy clusters help form these cosmic lenses, deflecting the light from objects obscured behind them due to their strong gravity. This effect, which is known as gravitational lensing, magnifies the properties of these hidden objects, allowing scientists to analyze them when such research would ordinarily have been impossible and allowing them to compare local galaxies with far more distant ones.

For this technique to work, however, the lensing galaxy in the foreground and the one being magnified need to be precisely aligned, which Messias said is a rare occurrence that is often hard to identify. However, he noted that recent studies have demonstrated they can be found more easily by conducting observations at far-infrared and millimeter wavelengths.

Galaxy H-ATLAS J142935.3-002836 (also known as H1429-0028), which was discovered in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), falls into this category. The study authors explain it is one of the brightest gravitationally lensed objects in the far-infrared regime discovered thus far, and is being observed at a time when the universe was approximately half of its current age.

[ Watch the Video: Artist’s Impression Of Gravitational Lensing Of A Distant Merger ]

After originally locating H1429-0028, the astronomers launched an extensive follow-up campaign that required the use of ALMA, Hubble, the Keck Observatory, the Karl G. Jansky Very Large Array (VLA) and other telescopes. By using so many different instruments, the research team was able to obtain several different views of the object, which they report could be combined to provide the best insight yet into the nature of these merging galaxies.

“ALMA enabled us to solve this conundrum because it gives us information about the velocity of the gas in the galaxies, which makes it possible to disentangle the various components, revealing the classic signature of a galaxy merger,” said Rob Ivison, ESO’s Director of Science and a co-author of the new study. “This beautiful study catches a galaxy merger red handed as it triggers an extreme starburst.”

“With the combined power of Hubble and these other telescopes we have been able to locate this very fortunate alignment, take advantage of the foreground galaxy's lensing effects and characterize the properties of this distant merger and the extreme starburst within it,” he added. “It is very much a testament to the power of telescope teamwork.”

Image 2 (below): This diagram shows how the effect of gravitational lensing around a normal galaxy focuses the light coming from a very distant star-forming galaxy merger to create a distorted, but brighter view. Credit: ESO/M. Kornmesser


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