Galactic bubbles are more complex than imagined
Fresh look at old data reveals novel details about galactic formation


Date:
May 8, 2023
Source:
Ohio State University
Summary:
Astronomers have revealed new evidence about the properties of the
giant bubbles of high-energy gas that extend far above and below
the Milky Way galaxy's center.


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

In a study recently published inNature Astronomy, a team led by scientists
at The Ohio State University was able to show that the shells of these structures -- dubbed "eRosita bubbles" after being found by the eRosita
X-ray telescope - are more complex than previously thought.

Although they bear a striking similarity in shape to Fermi
bubbles, eRosita bubbles are larger and more energetic than their
counterparts. Known together as the "galactic bubbles" due to their size
and location, they provide an exciting opportunity to study star formation history as well as reveal new clues about how the Milky Way came to be,
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 exist in the gas that surrounds galaxies, an area which
is 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,"
Gupta said.

"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." Previous studies
had assumed that these bubbles were heated by the shock of gas as it
blows outward from the galaxy, but this paper's main findings suggest the temperature of the gas within the bubbles isn't significantly different
from the area outside of it.

"We were surprised to find that the temperature of the bubble region and
out of the bubble region were the same," said Gupta. Additionally, the
study demonstrates that these bubbles are so bright because they're filled
with extremely dense gas, not because they are at hotter temperatures
than the surrounding environment.

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

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

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

"Our data supports the theory that these bubbles are most 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 continue characterizing the properties of these bubbles,
as well as work on novel ways to analyze the data they already have.

"Scientists really do need to understand the formation of the bubble
structure, so by using different techniques to better our models, we'll
be able to better constrain the temperature and the emission measures
that we are looking for," said Gupta.

Other co-authors were Joshua Kingsbury and Sanskriti Das of Ohio State
and Yair Krongold of the National Autonomous University of Mexico. This
work was supported by NASA.

* RELATED_TOPICS
o Space_&_Time
# Galaxies # Black_Holes # Astronomy # Astrophysics #
Stars # Solar_System # Extrasolar_Planets # NASA
* RELATED_TERMS
o Spitzer_space_telescope o Milky_Way o Magellanic_Clouds
o Local_Group o Globular_cluster o Planetary_nebula o
Barred_spiral_galaxy o Interstellar_medium

========================================================================== Story Source: Materials provided by Ohio_State_University. Original
written by Tatyana Woodall. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Anjali Gupta, Smita Mathur, Joshua Kingsbury, Sanskriti Das, Yair
Krongold. Thermal and chemical properties of the eROSITA
bubbles from Suzaku observations. Nature Astronomy, 2023; DOI:
10.1038/s41550-023- 01963-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230508150940.htm

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