Galactic bubbles most likely formed due to intense star formation activity rather than black hole: Study

A research team led by scientists at The Ohio State University has found new details about galactic bubbles, giant structures or regions of energized gas that extend far above and below our galaxy's centre. The team was able to show that the shells of these bubbles are more complex than previously thought.

Dubbed eRosita bubbles (detected by the eRosita X-ray telescope, hence the name), these structures bear a striking similarity in shape to Fermi bubbles but are larger and more energetic than their counterparts.

Together referred to as the "galactic bubbles", they provide valuable insights into the processes that shape galaxies and their evolution over time. 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 place very important in understanding how our galaxy formed and evolved. A lot of the regions that we were studying happened to be in the region of the bubbles, so we wanted to see how different the bubbles are when compared to the regions which are away from the bubble," 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.

The researchers analysed data from the Suzaku satellite, a collaborative mission between NASA and the Japanese Aerospace Exploration Agency (JAXA). By meticulously analyzing 230 archival observations made between 2005 to 2014, they characterized the diffuse emission, which refers to the electromagnetic radiation emitted by very low-density gas, of the galactic bubbles.

The origins of these expansive bubbles have long been a subject of debate among researchers, but this study represents a significant step towards resolving the issue, said Smita Mathur, co-author of the study and a professor of astronomy at Ohio State.

The team discovered an abundance of non-solar neon-oxygen and magnesium-oxygen ratios within the shells of the bubbles. This compelling evidence strongly indicates that the galactic bubbles were formed as a result of nuclear star-forming processes or the injection of energy by massive stars and other astrophysical phenomena as opposed to the activities of a supermassive black hole.

The researchers are eager to use new data from other upcoming space missions to continue characterizing the properties of galactic bubbles. They also plan to work on novel ways to analyze the existing data.

The study is published in the journal Nature Astronomy.