Scientists may have solved a huge galaxy mystery
It was a banner time for black hole Research: In recent months, astrophysicists have announced the discovery of the most powerful gamma-ray burst ever recorded (due to the formation of a black hole), a monstrous black hole in our cosmic backyard, the frame-dragging effects of a binary black hole, and the remains of the 2017 Kilonova event (spoiler alert: it was a black hole).
And with the help of citizen scientists, a team of astronomers recently discovered a unique black hole in a galaxy about a billion light-years away swinging one relativistic fighter jet at another universe.
The research was conducted by a team led by Ananda Hota, researcher at the UM-DAE Center for Excellence in Basic Sciences. The article describing their findings was published Oct. 12 in the Monthly Notices of the Royal Astronomical Society Letters.
Galaxies are generally divided into three main classes based on size, shape and composition. First, there are elliptical galaxies, which account for about a third of all the galaxies in the universe, ranging from nearly circular to very elongated.
Then there are the spiral galaxies, known for their distinct spiral arms and which look like flat disks with large yellowish bulges in their centers. Finally, there are irregular galaxies, which are neither elliptical nor spiral, and which were more common in the early Universe (before evolving into the other two classes).
When it comes to elliptical galaxies, astronomers have observed that the formation of new stars is very scarce and seems to have largely disappeared billions of years ago.
While the reason for this remains a mystery, modern research suggests the presence of supermassive black holes (SMBH) could be responsible.
These “monster black holes” cause the centers of massive galaxies to become Active Galactic Nuclei (AGN) – alias. Quasars – where the core is more energetic than all the stars in the disk combined.
In many cases, AGNs also have huge jets that spew from their poles and accelerate gas and dust to relativistic speeds (close to the speed of light). Ejecting this matter to other galaxies would deplete elliptical galaxies of the cold gas and dust that would otherwise fuel star formation.
Another mystery facing astronomers is how these AGN-powered jets link to the gas of merging galaxies, causing positive feedback. This temporarily leads to enhanced star formation, followed by negative feedback and a decrease in star formation.
To tackle this latest mystery, Dr. Hota and his colleagues found the SMBH in the center of RAD12, an elliptical galaxy about 1 billion light-years from Earth.
This uniqueness of this galaxy first became apparent in 2013 based on optical data from the Sloan Digitalized Sky Survey (SDSS) and radio data from the Very Large Arrays (VLA) Vague images of the radio sky at twenty centimeters (FIRST) survey.
But when Dr. Hota and his team re-observed it using the Giant Meter Wave Radio Telescope (GMRT) in India, they noticed that RAD12 seemed to eject matter from only one pole.
These observations were confirmed using radio and optical archival data from the MeerKAT array in Australia and the Canada-France-Hawaii Telescope (respectively). Unlike other jets that eject matter in pairs and in opposite directions, RAD12 seemed to eject matter only to its neighboring galaxy, RAD12-B.
Their observations also revealed a jet of young plasma that is conical in shape at the stem and flares out to become mushroom-shaped at the end (shown above). The yellow features represent galaxies — the larger ones are RAD12 (left) and RAD12-B (right) — and the plasma beam is shown in red.
The entire structure stretches 440,000 light-years and is much larger than the host galaxy itself. This is the first time a fighter jet has collided with a large galaxy such as RAD12-B. Like dr. Hota said in a recent Royal Astronomical Society (RAS) press release:
“We are pleased to have seen a rare system that helps us understand radio jet engine feedback from supermassive black holes to galaxy star formation during mergers. Observations from the GMRT and data from several other telescopes such as the MeerKAT radio telescope strongly suggest that the radio beam in RAD12 collides with the companion galaxy. An equally important aspect of this research is demonstrating public participation in making discoveries through [email protected] Citizen Science research collaboration.”
Thanks to the observations of Dr. Hota and his team are now taking astronomers one step closer to understanding the impact such interactions have on elliptical galaxies.
Their findings could lead to a new understanding of how star formation is halted in elliptical galaxies, solving a long-standing mystery about galactic evolution.
It is also a testament to the kind of research made possible today through collaboration between citizen scientists and astronomers.
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