Scientists Spot Debris from Colliding Galaxies

An international team of astronomers has imaged new tidal galactic-debris, stripped away from colliding galaxies. These new images are of special interest, since they tell the ancient story of galaxies’ collisions and the resultant starburst activities. According to the scientists, such astronomical events are important in order to understand how galaxies were ‘growing’ in the early universe.
 Deep optical image of Arp 220. New tidal debris is seen as the southern extension --doubling the size of the object from previously-known (Credit: Stony Brook University)
Deep optical image of Arp 220.
New tidal debris is seen as the southern
extension – doubling the size of the
object from previously-known
(Credit: Stony Brook University)

The study took place at the National Astronomical Observatory of Japan (NAOJ), using the 8.2-meter Subaru telescope on Mauna Kea, Hawaii. The team took extremely deep exposures of archetypal colliding galaxies; among the galaxies viewed were “the Antennae” galaxies in the constellation Corvus, “Arp 220″ in the constellation Serpens, and “Mrk 231″ in the constellation Big Dipper. The latter is as far as 590 million light years away, and like most of the galaxies chosen for this research it often appears in public media and textbooks. The reason for this kind of selection is that these galaxies are well known for their collisions’ history.

Colliding galaxies eventually merge, and become a single galaxy. When the orbit and rotation synchronize, galaxies merge quickly. Therefore, the researchers inferred that new tidal tails indicate quicker merging, which could be the trigger of starburst activities in Ultra Luminous Infrared Galaxy (ULIRG). “We did not expect such enormous debris fields around these famous objects,” says Dr. Koda, Assistant Professor of Astronomy at Stony Brook University. “For instance, the Antennae – the name came from its resemblance of insect ‘antennae’ – was discovered early in 18th century by William Herschel, and has been observed repeatedly since then.”

Dr. Taniguchi, a Professor at Ehime University in Japan, has elaborated on the importance of Ultra Luminous Infrared Galaxies. “ULIRGs are very likely the dominant mode of cosmic star formation in the early Universe, and Arp 220 is the key object to understand starburst activities in ULIRGs.”

Although galactic collisions are one of the most critical processes in galaxy formation and evolution in the early Universe, not all of them create such massive tidal debris. Dr. Koda has pointed out the important elements that affect the magnitude of these ‘tides’. “The orbit and rotation of colliding galaxies are the keys; theory predicts that large debris is produced only when the orbit and galactic rotation synchronize each other.”

Another participant in this project is Dr. Scoville, Professor of Astronomy at the California Institute of Technology. “The new images allow us to fully chart the orbital paths of the colliding galaxies before they merge, thus turning back the clock on each merging system,” he explained. “This is equivalent to finally being able to trace the skid marks on the road when investigating a car wreck.”

Dr. Koda emphasized that the extent of the debris seen had not been sighted in earlier imaging of these famous objects. “Subaru’s sensitive wide-field camera was necessary to detect and properly analyze this faint, huge, debris,” he compliments NAOJ’s telescope. “In fact, most debris is extended a few times bigger than our own Galaxy. We were ambitious to look for unknown debris, but even we were surprised to see the extent of debris in many already famous objects.”

The novel conclusions of this research will be presented at the 214th annual American Astronomical Society meeting in Pasadena, California. While they lead to better understanding of our Universe, all of the researchers involved in this study have agreed that further studies and detailed comparison with theoretical models are necessary in order to fully understand the observed phenomenon.

TFOT has previously covered a novel theory proposing a different approach towards galaxies’ origins, developed by scientists at the Hebrew University of Jerusalem, and the capturing of galaxy clusters collision using the Hubble Space Telescope and the Chandra X-Ray Observatory. Other related TFOT stories cover the light echo of an enormous X-ray flare, an event offering researchers a new method for mapping galactic nuclei, and the formation of massive stars, occurring with “help” from smaller stars surrounding them.

For more information about the discovery of the new tidal debris, see Stony Brook’s press release.

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