Amazing fusions of galaxies in the dawn of the universe

Two cutting-edge telescopes have been used to observe the confines of the universe and in doing so they have discovered a cosmic collision of epic proportions. When the universe was only 10% of its current age, 14 galaxies ended up colliding with each other, creating a megafusion that is detailed in the journals Nature and Astrophysical Journal thanks to the work of two teams. Thus, astronomers have witnessed the beginnings of a gigantic cosmic agglomeration.

This megafusion is destined to evolve into one of the most massive structures in the known universe: a group of colossal galaxies, gravitationally bound by dark matter and swimming in a sea of hot ionized gas.

The ALMA interferometer (Atacama Large Millimeter / submillimeter Array) and the APEX (Atacama Pathfinder Experiment) experiment have investigated the depths of space until the time when the universe was about 1,400 million years old. Finding a surprisingly dense concentration of 14 galaxies ready to merge has surprised the experts.

This figure highlights galaxies discovered by ALMA that are evolving into a galaxy cluster. The outer field is from data taken by the Hershel Space Observatory. The middle image, from a survey by the National Science Foundation’s South Pole Telescope, uncovered the distant galactic source that revealed 14 galaxies. Source: SciTechDaily

It is the most active area ever observed in the young universe.

The individual galaxies of this event are forming stars about 50-1,000 times faster than our galaxy (they are known as starburst galaxies) and are 'compressed' within a region of space about three times the size of the Milky Way. The resulting cluster of galaxies will eventually rival some of the most massive clusters we see today in the universe.

The system, called SPT2349-56, is considered a proto-cumulus and the merger occurs 1.5 billion years after the Big Bang. As these galaxies merge, they will form a single massive galaxy, probably the progenitor of the galaxies of the central cluster that we see in the universe today.

Source: Nature.

"How this set of galaxies got so big and so fast is a mystery, it did not build up gradually over billions of years, as astronomers would expect," said Tim Miller of Yale University and leader of the work. "This discovery provides a great opportunity to study how massive galaxies came together to build huge clusters of galaxies."

"It is believed that the duration of dusty starburst outbreaks is relatively short, since they consume gas at an extraordinary rate." At any time, in any corner of the universe, these galaxies tend to be a minority, so find numerous outbreaks. of dusty star formation shining at the same time in that way is very disconcerting, and something that we still need to understand, "says Ivan Oteo of the University of Edinburgh and leader of the other team.

The galaxies were discovered for the first time as very weak objects by instruments such as the South Pole Telescope and the observatory of the European Space Agency Herschel. Subsequent observations revealed that the light spots were not unique galaxies, but were actually megafusions with many galactic members.

This montage shows three views of SPT2349-56. The left image is a wide view from the South Pole Telescope that reveals just a bright spot. The central view is from APEX that reveals more details. The right picture is from ALMA and reveals that the object is actually a group of 14 merging galaxies in the process of forming a galaxy cluster. Image credit: ESO / ALMA / NAOJ / NRAO / Miller et al. Source: Sci-News

"These ALMA discoveries are just the tip of the iceberg," comments Carlos De Breuck, astronomer at the European Southern Observatory. "Additional observations with the APEX telescope show that the actual number of star-forming galaxies is probably even three times greater."

The primitive universe is still full of unknowns, but finally (and literally) we see some light in the dark.

Reference:
T.B. Miller et al. 2018. A massive core for a cluster of galaxies at a redshift of 4.3. Nature 556: 469-472; doi: 10.1038/s41586-018-0025-2
I. Oteo et al. 2018. An Extreme Protocluster of Luminous Dusty Starbursts in the Early Universe. ApJ 856, 72; doi: 10.3847/1538-4357/aaa1f1