Mystery Galaxy with an 800,000 Light-Year Long Tail

GalaxyClusterTails

The latest discovered of such intergalactic violence a galaxy called not too poetically as FGC 1287 located at the edge of a cluster of other galaxies. New radio evidence from the Very Large Array in New Mexico has revealed that it is bleeding a vast trail of gas stretching across 800,000 light years of dark space, leeched by "headwinds" created as the galaxy moves through a galaxy cluster's own gas.


"When we looked at the data, we were amazed," says Tom Scott of the Andalucia Institute of Astrophysics in Granada, Spain, who led the study.

The tail is made of billions of suns' worth of hydrogen gas that has somehow escaped from FGC 1287 – more gas than remains in the galaxy itself.

"FGC 1287 is completely different from any case we have seen before," says team member Luca Cortese of the European Southern Observatory in Garching, Germany. X-ray observations of the cluster's gas, however, suggest it is too thin at FGC 1287's location to make the galaxy feel much of a wind, says the team.

A near miss with another galaxy might be a better lead and could explain why the galaxy's stars are not in disarray. In a brief encounter at high speed, the second galaxy's gravity could have pulled away loosely bound gas without disturbing its stars, which are more tightly bound to the galaxy by gravity.

The case is not closed, however, because the suspect galaxy looks much less massive and shows no sign of trauma itself. It is not clear how it could have made such a large impact on the heavier galaxy without being transformed itself.

Whatever the solution to the nystery, the team say the case suggests we have a lot to learn about how violence effects galaxies. Perhaps FGC 1287 is enduring stronger winds than expected, or another galaxy not obviously connected to it will turn out to be its enemy.

"This discovery might open a new chapter in our understanding of environmental effects on galaxy evolution," says team member Elias Brinks of the University of Hertfordshire, UK.

The Daily Galaxy via Monthly Notices of the Royal Astronomical Society: Letters, DOI: 10.1111/j.1745-3933.2011.01169.x

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