Astronomers have revealed new clues about the properties of giant bubbles of high-energy gas that extend above and below the center of the Milky Way galaxy.
In a study recently published innatural astronomya team led by scientists at Ohio State University has been able to show that the shells of these structures – dubbed “eRosita bubbles” after they were found by the eRosita X-ray telescope – are more complex than previously thought.
Although they bear a striking resemblance in shape to Fermi bubbles, eRosita bubbles are larger and more energetic than their counterparts. said Anjali Gupta, lead author of the study and a former postdoctoral researcher at Ohio State who is now a professor of astronomy at Columbus State Community College.
These bubbles are found in the gas that surrounds galaxies, a region called the circumgalactic milieu.
“Our goal was really to learn more about the galactic medium, which is a very important place in understanding how our galaxy formed and evolved,” said Gupta. “A lot of the regions we were studying happened to be in the bubble area, so we wanted to see how different the bubbles were when compared to the regions farther from the bubble.”
Previous studies hypothesized that these bubbles were heated by the shock of the gas as it spiraled outward from the galaxy, but the main findings of this paper indicate that the temperature of the gas inside the bubbles does not differ significantly from the region outside it.
“We were surprised that the temperature of the bubble area and outside the bubble area was the same,” said Gupta. In addition, the study shows that these bubbles are so bright because they are filled with a very dense gas, and not because they are at higher temperatures than the surrounding environment.
Gupta and Smita Mathur, co-authors of the study and a professor of astronomy at Ohio State, analyzed them using observations made by the Suzaku satellite, a collaborative mission between NASA and the Japan Aerospace Exploration Agency.
By analyzing 230 archival observations made between 2005 and 2014, the researchers were able to characterize the diffuse emissions — electromagnetic radiation from extremely low-intensity gas — of the galactic bubbles, as well as the other hot gases that surround them.
Mathur said that although the origin of these bubbles has been discussed in the scientific literature, this study is the first to begin to unravel it. Because the team found an abundance of non-solar oxygen-magnesium-oxygen ratios in the shells, their results strongly suggest that the galactic bubbles were originally formed through nuclear star formation activity, or by injections of massive stars and other types of energy. By astrophysical phenomena, not by the activities of the supermassive black hole.
“Our data support the theory that these bubbles are likely formed due to intense star-forming activity at the center of the galaxy, as opposed to black hole activity that occurs at the center of the galaxy,” said Mathur. To further investigate what implications their discovery might have on 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 new ways to analyze the data they already have. .
“Scientists really need to understand the formation of bubble structure, so by using different techniques to improve our models, we will be able to better constrain the temperature and emission procedures that we are looking for,” said Gupta.
Other co-authors are Joshua Kingsbury and Sanskrit Das of Ohio State and Yair Krongold of the National Autonomous University of Mexico. This work was supported by NASA.