Astronomers have revealed new evidence about the properties of giant bubbles of high-energy gas that extend far above and below the center of the Milky Way galaxy.

In a study published in Nature Astronomy, a team led by Ohio State University scientists was able to show that the layers of these structures, dubbed “eRosita bubbles” after they were found by the eRosita X-ray telescope, are more complex than expected. that had previously been estimated.

Although they bear a striking similarity in shape to Fermi bubbles, eRosite bubbles are larger and more energetic than their counterparts. Collectively known as “galactic bubbles” because of their size and location, they provide an exciting opportunity to study the history of star formation and reveal new clues about how the Milky Way came to be, said Anjali Gupta, lead author of the study and former postdoctoral researcher at Ohio State who is now a professor of astronomy at Columbus State Community College.

These bubbles exist in the gas surrounding galaxies, an area called the circumgalactic medium. “Our goal was really to learn more about the circumgalactic medium, a very important place to understand how our galaxy formed and evolved,” Gupta said in a statement. “Many of the regions we were studying were in the region of the bubbles, so we wanted to see how different the bubbles are compared to regions that are far from the bubble.”

Although they bear a striking similarity in shape to Fermi bubbles, eRosite bubbles are larger and more energetic than their counterparts. Collectively known as “galactic bubbles” because of their size and location, they provide an exciting opportunity to study the history of star formation and reveal new clues about how the Milky Way came to be, said Anjali Gupta, lead author of the study and former postdoctoral researcher at Ohio State who is now a professor of astronomy at Columbus State Community College.

These bubbles exist in the gas surrounding galaxies, an area called the circumgalactic medium. “Our goal was really to learn more about the circumgalactic medium, a very important place to understand how our galaxy formed and evolved,” Gupta said in a statement. “Many of the regions we were studying were in the region of the bubbles, so we wanted to see how different the bubbles are compared to regions that are far from the bubble.”

Previous studies had assumed that these bubbles were heated by the colliding of the gas as it blew out of the galaxy, but the main findings of this paper suggest that the temperature of the gas inside the bubbles is not significantly different from that of the outer area. .

“We were surprised to find that the temperature in the bubble region and outside the bubble region were the same,” Gupta said. Furthermore, the study shows that these bubbles are so bright because they are filled with extremely dense gas, not because they are at higher temperatures than their surrounding environment.

Gupta and Smita Mathur, study co-author and professor of astronomy at Ohio State, conducted their analysis using observations made by the Suzaku satellite, a collaborative mission between NASA and the Japan Aerospace Exploration Agency (JAXA).

By analyzing 230 archival observations made between 2005 and 2014, the researchers were able to characterize the diffuse emission (the electromagnetic radiation from very low-density gas) from the galactic bubbles, as well as other hot gases surrounding them.

Although the origin of these bubbles has been debated in the scientific literature, this study is the first to begin to unravel it, Mathur said. As the team found a large number of non-solar neon-oxygen and magnesium-oxygen ratios in the layers, their results strongly suggest that the galactic bubbles originally formed by nuclear star-forming activity, or the injection of energy by from massive stars and other types of astrophysical phenomena, rather than through the activities of a supermassive black hole.

“Our data support the theory that these bubbles likely formed due to intense star formation activity at the galactic center, as opposed to black hole activity occurring at the galactic center,” Mathur said. To further investigate the implications their discovery may have for other aspects of astronomy, the team hopes to use new data from other upcoming space missions to further characterize the properties of these bubbles, as well as work on novel ways to analyze the data they they already have.

source: https://www.nature.com/articles/s41550-023-01963-5