A black hole hurls a jet of material at its neighboring galaxy

It was an excellent time for black hole exploration! In recent months, astrophysicists have unveiled the discovery of the most powerful gamma-ray burst ever recorded (due to black hole formation), a monster black hole in our cosmic backyard, the frame drag effects of a binary black hole, and the remnants 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, hurling a relativistic beam at another galaxy.

The research was conducted by a team led by Ananda Hota, a researcher at the UM-DAE Center for Excellence in Basic Sciences. He was joined by researchers from the Indian Institute of Astrophysics, Sorbonne University’s Laboratory for the Study of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Arecibo Observatory, Amity Institute of Applied Sciences, Thapar Institute of Engineering and Technology, and the [email protected] Citizen Science Collaboration. The paper describing their findings was published October 12 in the Monthly Bulletins of the Royal Astronomical Society Letters.

Galaxies are typically divided into three main classes based on size, shape, and composition. First, there are elliptical galaxies, which make up about a third of all galaxies in the universe, ranging from nearly circular to very elongated. Then there are spiral galaxies, known for their distinct spiral arms, appearing as flat discs with large yellowish bulges at their centers. Finally, there are irregular galaxies, which are neither elliptical nor spiral, that were more common in the early Universe (before evolving into the other two classes).

Regarding elliptical galaxies, astronomers have observed that the formation of new stars is very rare and appears to have largely stopped billions of years ago. While the reason for this remains a mystery, modern research suggests that the presence of supermassive black holes (SMBH) could be to blame. These “monster black holes” cause the centers of massive galaxies to become active galactic nuclei (AGN) – also known as. Quasars – where the core is more energetic than all the stars in the disk combined.

In many cases, AGNs also have massive jets emanating from their poles, accelerating gas and dust to relativistic velocities (near the speed of light). The ejection of this matter toward other galaxies is thought to strip elliptical galaxies of the cold gas and dust that would otherwise fuel star formation. Another mystery astronomers face is how these AGN-driven jets couple with the gas of merging galaxies, causing positive feedback. This temporarily leads to increased star formation, followed by negative feedback and a drop in star formation.

To solve this final mystery, Dr. Hota and his colleagues found the SMBH at the center of RAD12, an elliptical galaxy about 1 billion light-years from Earth. This unique nature of this galaxy was first revealed in 2013 using optical data from the Sloan Digitized Sky Survey (SDSS) and radio data from the Very Large Array VLA survey Faint Images of the Radio Sky at Twenty-Centimeters (FIRST). But as dr. Observing it again with the Giant Meterwave Radio Telescope (GMRT) in India, Hota and his team found that RAD12 appeared to be ejecting matter from only one pole.

These observations were corroborated by archived radio and optical data from the MeerKAT array in Australia and the Canada-France-Hawaii telescope, respectively. Unlike other jets, which eject matter in pairs and in opposite directions, RAD12 appeared to be ejecting matter only in the direction of its neighboring galaxy, RAD12-B. Their observations also revealed a jet of young plasma that is conical in shape at the stalk and flares out like a mushroom at the end (see above). The yellow features represent galaxies – the larger ones are RAD12 (left) and RAD12-B (right) – and the plasma jet is shown in red.

The entire structure spans 440,000 light-years and is much larger than the host galaxy itself. This is the first time a jet has collided with a large galaxy like RAD12-B. like dr Hota said in a recent Royal Astronomical Society (RAS) press release:

“We are pleased to have discovered a rare system that will help us understand the radiojet feedback from supermassive black holes on galaxy star formation during mergers. Observations with the GMRT and data from various other telescopes such as the MeerKAT radio telescope strongly suggest that the radio jet in RAD12 collides with the companion galaxy. An equally important aspect of this research is the demonstration of public participation in discoveries by the [email protected] Citizen Science Research Collaboration.”

Thanks to the observations of Dr. Hota and his team have now taken astronomers a step closer to understanding the effects such interactions have on elliptical galaxies. Their findings could lead to a new understanding of how star formation is halted in elliptical galaxies and solve a long-standing mystery of galactic evolution. It’s also a testament to the kind of research possible today through collaboration between citizen scientists and astronomers.

Further reading: RA