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The question of what triggers the extremely rapid star formation in ultraluminous infrared galaxies (HyLIRGs), still unknown, is of great interest to guide our understanding of the formation and evolution of galaxies in the Universe. A new image released by the European Southern Observatory shows a HyLIRG 10,000 times brighter than our Milky Way (in infrared light) – the distant galaxy PJ0116-24 – and was published in conjunction with a recently published article in Natural astronomy which sheds light on its formation.

Previous studies suggested that such extremely bright galaxies must be the result of galaxy mergers. These galaxy collisions are thought to create regions of dense gas in which rapid star formation is triggered. But isolated galaxies could also become HyLIRGs only through internal processes, if the star-forming gas were rapidly funneled towards the center of the galaxy.

In the paper, titled “Detailed Study of a Rare Superluminous Rotating Disk in an Einstein Ring 10 Billion Years Ago,” in which Cornell astronomer Amit Vishwas, Ph.D. is a co-author, observations from ESO’s Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA) were combined to study the motion of gas in PJ0116-24.

ALMA tracks cold gas, seen in the picture in blue, while the VLT, with its new Imager and Enhanced Resolution Spectrograph (ERIS), tracks warm gas, shown in red. Thanks to these detailed observations, the international research team discovered that the gas in this extreme galaxy rotates in an organized manner, rather than the chaotic manner expected after a galactic collision – a surprising result. This shows, the researchers said, that mergers are not always necessary for a galaxy to become a HyLIRG.

PJ0116-24 is so far away that its light took about 10 billion years to reach us. A foreground galaxy acted as a gravitational lens, bending and magnifying the light of PJ0116-24 behind it into the Einstein ring seen here. This precise cosmic alignment allows astronomers to zoom in on very distant objects and see them with a level of detail that would otherwise be very difficult to achieve.

Vishwas, a research associate at the Cornell Center for Astrophysics and Planetary Sciences (CCAPS), helped map the emission and kinematics from atomic and molecular gas in PJ0116-24 using ALMA, which provided strong support for the rotating disk scenario. It is also involved in the acquisition of data with the VLT’s newly commissioned ERIS instrument. The research was led by Daizhong Liu of the Max Planck Institute for Extraterrestrial Physics and the Purple Mountain Observatory.

The interpretation of the gas conditions and elemental abundances in PJ0116-24 is similar to what Vishwas and his co-authors reported last year for another galaxy at an earlier age in the Universe, using data from the James Webb Space Telescope.

However, PJ0116-24 is about five times more massive and luminous than the source studied in last year’s paper, Vishwas said.

“In both cases, gravitational lensing helped us zoom in to study the details of the interstellar medium of these galaxies. “I believe these new observations help us build a case for the way galaxies evolve and form – effectively turning gas into stars in rapid growth spurts separated by long periods of relative quiescence,” he explained.