Astronomers Discover Spheroid Formation Process in Early Universe

The discovery was through use of the Atacama Large Millimeter/Submillimeter Array (ALMA) telescope, according to an article published in the academic journal Nature.

The discovery was led by Purple Mountain Observatory (PMO) under the Chinese Academy of Sciences, and involved significant participation from CEA Paris-Saclay and University of Tokyo.

In the early universe, there was a special type of galaxy called a starburst galaxy. These galaxies were able to produce new stars and caused rapid and extreme supernova explosions -- which eventually resulted in the formation of supermassive black holes at their cores. The cores of most galaxies contained a dense central region made up of many stars called spheroids. However, it was previously unclear how these spheroids formed.

In the study led by PMO, researchers used statistical analysis of the surface brightness distribution of dust emissions in the submillimeter band. The data analyzed was provided by the ALMA telescope, which observed over 100 luminous starburst galaxies dating back to the cosmic noon era, which was between around 8 and 12 billion years ago and was a period when many galaxies were actively forming stars.

"The analysis showed that most of these highly star-forming galaxies were intrinsically spherical rather than disk-shaped," said Tan Qinghua, associate researcher from the PMO and also the study's corresponding author.

A further numerical simulation suggested that the main mechanism behind the formation of these spheroids was the simultaneous action of cold gas accretion and galaxy interactions. This process was thought to have been quite common in the early universe -- the period when most spheroids formed.

According to Tan, the study provides the first solid observational evidence that spheroids could form directly through intense star formation within the cores of highly luminous starburst galaxies in the early universe -- which may have significantly impacted the morphology and evolution of galaxies, ultimately forming the elliptical galaxies found in today's universe.

"In the future, via the application of more advanced observational equipment with higher resolution and sensitivity, scientists may gain a more complete picture of the galaxy formation process in the early universe, thereby deepening our understanding of how the entire universe evolved over time," Tan said.

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