A team of astronomers using ESA’s Herschel Space Observatory has discovered a giant, galaxy-packed filament ablaze with billions of new stars.
Three galaxy clusters of the emerging supercluster RCS2319 are seen in visible and X-ray light (purple) to the left. Observations by Herschel in infrared light appear to the right, with colored regions indicating greater infrared emissions. A white circle broadly outlines the 8 million light-year-long intergalactic filament in each image (ESA / NASA / JPL-Caltech / CXC / McGill University)
The intergalactic filament connects two clusters of galaxies that, along with a third cluster, will smash together and give rise to one of the largest galaxy superclusters in the Universe. This structure is the first of its kind spied in a critical era of cosmic buildup when colossal collections of galaxies called superclusters began to take shape.
Containing hundreds of galaxies, the filament spans 8 million light-years and links two of the three clusters that make up a supercluster known as RCS2319. This emerging supercluster is an exceptionally rare, distant object whose light has taken more than seven billion years to reach us.
“We are excited about this filament, because we think the intense star formation we see in its galaxies is related to the consolidation of the surrounding supercluster,” said Dr Kristen Coppin, a postdoctoral fellow in astrophysics at McGill University and lead author of a new paper, which will be published in Astrophysical Journal Letters.
“This luminous bridge of star formation gives us a snapshot of how the evolution of cosmic structure on very large scales affects the evolution of the individual galaxies trapped within it,” added Dr Jim Geach of McGill University, a co-author of the research.
Previous observations of RCS2319 in visible and X-ray light had found the cluster cores and hinted at the presence of a filament. It was not until astronomers trained Herschel on the region, however, that the intense star-forming activity in the filament became clear. Dust obscures much of the star-formation activity in the early universe, but telescopes like Herschel can detect the infrared glow of this dust as it is heated by nascent stars.
The amount of infrared light suggests that the galaxies in the filament are cranking out the equivalent of about 1,000 solar masses (the mass of our Sun) of new stars per year. For comparison’s sake, our Milky Way galaxy is producing about one solar mass-worth of new stars per year.
Researchers chalk up the blistering pace of star formation in the filament to the fact that galaxies within it are being crunched into a relatively small cosmic volume under the force of gravity. “A high rate of interactions and mergers between galaxies could be disturbing the galaxies’ gas reservoirs, igniting bursts of star formation,” Dr Geach explained.
By studying the filament, astronomers will be able to explore the fundamental issue of whether “nature” versus “nurture” matters more in the life progression of a galaxy. “Is the evolution of a galaxy dominated by intrinsic properties such as total mass, or do wider-scale cosmic environments largely determine how galaxies grow and change?” Dr Geach asked. “The role of the environment in influencing galactic evolution is one of the key questions of modern astrophysics.”
