Two state-of-the-art telescopes have been employed to observe the far reaches of the universe and in doing so have discovered a cosmic collision of epic proportions . When the universe was just 10% of its current age, 14 galaxies ended up colliding with each other, creating a mega-fusion 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 mega-fusion is destined to evolve into one of the most massive structures in the known universe : a group of colossal galaxies, bound gravitationally by dark matter and swimming in a sea of hot ionized gas.
With the ALMA ( Atacama Large Millimeter / submillimeter Array ) interferometer and the APEX ( Atacama Pathfinder Experiment) experiment, scientists have probed the depths of space up to the time when the universe was about 1.4 billion years old. Finding a surprisingly dense concentration of 14 galaxies ready to merge has surprised experts.
It is the most active zone ever observed in the young universe
The individual galaxies in this event are forming stars about 50-1,000 times faster than our galaxy (known as starburst galaxies) and are ‘squeezed’ within a region of space roughly three times the size of the Milky Way. The resulting galaxy cluster will eventually rival some of the most massive clusters we see in the universe today.
The system, named SPT2349-56 , is considered a protocluster 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 central cluster galaxies we see in the universe today.
“ How this collection of galaxies got so big and so fast is a mystery. It did not accumulate gradually over billions of years, as astronomers might 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 galaxy clusters.”
“The duration of dusty starbursts is believed to be relatively short, as they consume the gas at an extraordinary rate. At any time, in any corner of the universe, these galaxies are usually in the minority. Therefore, find numerous outbreaks dusty star formation shining at the same time like that is very disconcerting, and something we still need to understand, “clarifies Iván Oteo from the University of Edinburgh and leader of the other team.
The galaxies were first discovered as very faint objects by instruments such as the South Pole Telescope and the European Space Agency’s Herschel Observatory. Subsequent observations revealed that the patches of light were not unique galaxies, but were actually mega-mergers with many galactic members.
“ These ALMA discoveries are just the tip of the iceberg,” says Carlos De Breuck, an 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 higher.”
The early universe is still full of unknowns, but finally (and literally) we see some light in the dark.
Referencia: A massive core for a cluster of galaxies at a redshift of 4.3, Nature (2018). nature.com/articles/doi:10.1038/s41586-018-0025-2
This research was presented in two papers, “The Formation of a Massive Galaxy Cluster Core at z = 4.3”, by T. Miller et al., to appear in the journal Nature, and “An Extreme Proto-cluster of Luminous Dusty Starbursts in the Early Universe”, by I. Oteo et al., which appeared in the Astrophysical Journal.
