Galaxies are typically divided into two major classes based on their morphology: spirals and ellipticals. In spiral galaxies, new stars form at an average rate of one Sun-like star per year. In contrast, star formation in elliptical galaxies is very scarce.
It remains unclear why the elliptical galaxies have not been forming new stars for billions of years. According to the evidence, supermassive or “monster” black holes may be at blame. These “monster” black holes release enormous electron jets traveling at very high speeds at distant galaxies, depleting the cool gas and dust needed for future star formation.
A team of astronomers has found a distinctive black hole that is shooting a fiery jet at another galaxy with the aid of citizen scientists. The black hole is housed in the RAD12 universe, around a billion light-years from Earth.
Using optical data from the Sloan Digitized Sky Survey (SDSS) and radio data from the Very Large Array, RAD12’s distinctive characteristics were discovered in 2013. (FIRST survey). However, follow-up observation with the Giant Meter wave Radio Telescope (GMRT) in India was required to confirm its truly exotic nature: Only a nearby galaxy known as RAD12-B appears to be receiving the jet from the black hole in RAD12. Jets are always ejected in pairs and travel at relativistic speeds in opposite directions. Astronomers are still perplexed as to why only one jet is observed to be originating from RAD12.
Beyond the RAD12 visible stars, a conical stem of young plasma may be seen blasted from the center. According to the GMRT observations, the older, fainter plasma erupts out like a mushroom cap from the center of the central conical stalk (seen in red in the tricolor image). The entire structure spans 440 thousand light-years, making it significantly longer than the host galaxy.
RAD12 is unlike anything known so far; this is the first time a jet has been observed to collide with a large galaxy like RAD12-B. Astronomers are one step closer to understanding the impact of such interactions on elliptical galaxies, which may leave them with little cold gas for future star formation.
Research lead Dr. Ananda Hota says, “We are excited to have spotted a rare system that helps us understand radio jet feedback of supermassive black holes on galaxies’ 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 is colliding with the companion galaxy. An equally important aspect of this research is the demonstration of public participation in making discoveries through the RAD@home Citizen Science research collaboratory.”
- Ananda Hota et al., RAD@home citizen science discovery of an active galactic nucleus spewing a large unipolar radio bubble on to its merging companion galaxy, Monthly Notices of the Royal Astronomical Society: Letters (2022). DOI: 10.1093/mnrasl/slac116