Gamma ray discovery could advance understanding of role of ultra-fast
outflows in the evolution of galaxies

Date:
November 10, 2021
Source:
Clemson University
Summary:
Using data gathered by the Large Area Telescope onboard NASA's
Fermi Gamma-ray Space Telescope and a stacking technique combining
signals too weak to be observed on their own, researchers detected
gamma rays from UFOs -- ultra-fast outflows -- in several nearby
galaxies, providing a basis for scientists to understand what
happened in our own Milky Way galaxy.



FULL STORY ========================================================================== Using data gathered by the Large Area Telescope onboard NASA's Fermi
Gamma-ray Space Telescope and a stacking technique combining signals too
weak to be observed on their own, researchers detected gamma rays from
UFOs in several nearby galaxies for the first time, providing a basis
for scientists to understand what happened in our own Milky Way galaxy.


==========================================================================
UFOs are ultra-fast outflows -- powerful winds launched from very near supermassive black holes that scientists believe play an important role
in regulating the growth of the black hole itself and its host galaxy.

Clemson University scientists' collaborative research is published in
The Astrophysical Journal. Partners include the College of Charleston,
the University of Chicago, and a host of other researchers who are part of
the Fermi-LAT Collaboration, which includes hundreds of scientists from 12 countries. "Gamma rays from Fast Black-Hole Winds" outlines the detection
of gamma-ray emission from UFOs launched by supermassive black holes.

"Although these winds are challenging to detect, it is thought that
they play a significant role in how a massive black hole and the host
galaxy itself grow," said Chris Karwin, a postdoctoral fellow in the
College of Science's Department of Physics and Astronomy and leader
of the study. "Our gamma-ray observations show how supermassive black
holes can transfer a large amount of energy to their host galaxy. These
UFOs create shock waves, which act like pistons and actually accelerate
charged particles, known as cosmic rays, to near the speed of light."
Every galaxy has a supermassive black hole at its center. Some are
dormant.

Others, called active galactic nuclei, are active, meaning that they draw
in and "eat" the surrounding matter through a process called accretion.

While traveling through the galaxies, the winds gradually disable star formation. "The effect on the galaxy is dramatic," said Marco Ajello,
associate professor in Clemson College of Science's Department of Physics
and Astronomy who is co-leading the study. "The black hole at the center
of the galaxy and the galaxy itself have a mechanism to grow together in
mass -- and this is the mechanism." Because the gamma rays detected are produced by cosmic rays accelerated at the shock front, Karwin said it
attests to the onset of the wind-host interaction and that the UFOs can energize charged particles up to the transition region between galactic
and extragalactic cosmic rays.



========================================================================== Understanding the Milky Way The findings of the study could help
scientists understand what happened in our own Milky Way galaxy.

Sagittarius A* is the supermassive black hole at the center of the Milky
Way with about 4 million times the sun's mass. Extending above and below
the Milky Way's disc are Fermi bubbles, enormous round structures of hot
gas emanating from the galactic center. They're called Fermi bubbles
because the Fermi Gamma- Ray Space Telescope, the source of the data
used by Ajello and Karwin in the current study, discovered them in 2010.

"Today, our black hole, Sagittarius A*, is not active, but it's possible
it was active in the recent past, maybe up until a few hundred years ago," Karwin said. "Our model supports the hypothesis that these Fermi bubbles
may be remnants of past UFO-like activity from the supermassive black
hole in the center of our galaxy." Ajello said future work includes
studying galaxies that have had active UFO winds for 10s of millions of
years that have already traveled to the outskirts of the galaxy.

This research was supported by the National Science Foundation and NASA
through grants AST-1715256 and 80NSSC18K1718.

========================================================================== Story Source: Materials provided by Clemson_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
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Bellazzini, A. Berretta, E. Bissaldi, R. D. Blandford, E. D. Bloom,
R.

Bonino, P. Bruel, S. Buson, R. A. Cameron, D. Caprioli, R. Caputo,
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Marcotulli, G. Marti'-Devesa, M. N. Mazziotta, I. Mereu,
P. F. Michelson, T. Mizuno, M. E. Monzani, A. Morselli,
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Omodei, M. Orienti, E. Orlando, V. Paliya, D. Paneque, Z. Pei,
M. Persic, M. Pesce-Rollins, T. A. Porter, G. Principe,
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Tak, D. F. Torres, E. Troja, K. Wood, G. Zaharijas, J. Zrake. Gamma
Rays from Fast Black-hole Winds. The Astrophysical Journal, 2021;
921 (2): 144 DOI: 10.3847/1538-4357/ac1bb2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211110104232.htm

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