ALMA Solves Mysteries of Jets from Giant Black Holes

Two international teams of astronomers explored the jets of molecular gas from giant black holes at the heart of galaxies and their impact on the surrounding space environment with the help of ALMA ( Atacama Large Millimeter/submillimeter Array).

The astronomers observed the presence of molecular gas around a quiet black hole in the galaxy named NGC 1433, situated close by. Another finding made by the researchers was the presence of a strong jet near a black hole named PKS 1830-211, located at a far off distance.

"ALMA has revealed a surprising spiral structure in the molecular gas close to the centre of NGC 1433," Françoise Combes, the lead author of the first paper, from Observatoire de Paris, France, stated in a press release.

"This explains how the material is flowing in to fuel the black hole. With the sharp new observations from ALMA, we have discovered a jet of material flowing away from the black hole, extending for only 150 light-years. This is the smallest such molecular outflow ever observed in an external galaxy," Combes added.

The black holes observed in this galaxy are enormous, weighing around several billion solar masses and presently they are less active than in the past. The interactions between the surrounding space and the jets are leading to further developments and changes in the galaxy.

The astronomers observed these black hole jets at varying scales. This finding portrays how powerful jets end star formations and regulate the expansion of the black holes present in the centre of the galaxy.

Ivan Marti-Vidal from Chalmers University of Technology, Onsala Space Observatory, Sweden, along with his team examined a supermassive black hole with a jet in PKS 1830-211, which was comparatively more active and brighter than the one observed in the early Universe.

This finding was remarkable as the dazzling light emitted by this jet passes by a giant galaxy on its way to Earth and splits into two images because of the gravitational lensing.

"The ALMA observation of this case of black hole indigestion has been completely serendipitous. We were observing PKS 1830-211 for another purpose, and then we spotted subtle changes of colour and intensity among the images of the gravitational lens," Sebastien Muller, a co-author of the second paper explained.

"A very careful look at this unexpected behaviour led us to the conclusion that we were observing, just by a very lucky chance, right at the time when fresh new matter entered into the jet base of the black hole," says Muller added.

The second observation led to the finding that super giant black holes suddenly suck up large quantities of matter, which fuels their radiation and boosts their energies. This phenomenon was accidentally captured by the ALMA.

The team tried finding out whether this phenomenal activity was captured by other telescopes and figured out that extremely clear gamma rays signals were received by them, NASA's Fermi Gamma-ray Space Telescope was being credited for recording these observations.

"This is the first time that such a clear connection between gamma rays and submillimetre radio waves has been established as coming from the real base of a black hole's jet," said Sebastien Muller.

Another active galaxy located nearby is presently being analyzed by Combes' team using ALMA and the unique black hole PKS 1830-211 is likely to be observed and analyzed more in the future research with ALMA and other telescopes.

"There is still a lot to be learned about how black holes can create these huge energetic jets of matter and radiation. But the new results, obtained even before ALMA was completed, show that it is a uniquely powerful tool for probing these jets -- and the discoveries are just beginning!" Ivan Marti-Vidal concluded.