Billions of light years away from the Earth is one of the most massive structures in the universe, a gigantic elliptical galaxy surrounded by a cluster of other galaxies known as Abell 2597. In the nucleus of the central galaxy, a supermassive black hole is fueling the 39, the cosmic equivalent of a monumental fountain, which draws on vast deposits of cold molecular gas and sprays them again in a continuous cycle.
Astronomers have long theorized that fountains like this continually recirculate the fuel that forms a star in the galaxy. The new Atacama Large Millimeter / submillimeter Array (ALMA) observations from Abell 2597 show the first clear and convincing evidence for simultaneous blocking and outflow of gas driven by a supermassive black hole. The researchers report their observations in the last issue of the Astrophysical diary.
"The supermassive black hole at the center of this gigantic galaxy acts like a mechanical" pump "in a water fountain," said Grant Tremblay, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, in Massachusetts, and principal author on the paper. "This is one of the first systems in which we find clear evidence both for the inflow of cold molecular gas towards the black hole, and for the outflow or lifting from the jets that the black hole launches".
According to the researchers, this whole system works via a self-regulating feedback loop. Falling material supplies energy to the fountain as it "unloads" to the central black hole, like water entering a fountain pump. This alarming gas then triggers the black hole with activity by throwing high-speed jets of overheated material that shoots out of the galaxy. As it travels, this material pushes lumps and flames of gas into the expansive aura of the galaxy, where it eventually rains again on the black hole, triggering the whole process again.
In total, about three billion solar molecules of molecular gas are part of this fountain, forming a filamentary nebula that extends over 100,000 light years of the galaxy.
In a previous study by the same authors published in the journal Nature, researchers were able to verify the interconnection between the black hole and the galactic fountain by observing the region through a range of wavelengths or portions of the spectrum . By studying the position and movement of carbon monoxide (CO) molecules with ALMA, which shine intensely in a millimeter-long light, researchers could measure the movement of the gas as it falls toward the black hole.
Previous data from the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) from the ESO revealed that hot ionized gas was being ejected from the galaxy, essentially the fountain's plume. The new ALMA observations found clumps of cold and molecular gas in exactly the same positions as the hot gas observed in the previous observations.
"The unique aspect here is a very detailed coupled analysis of the source that uses the data from ALMA and the MUSE instrument: the two structures offer an incredibly powerful combination," said Tremblay. "ALMA revealed the distribution and motions of cold molecular gas clouds, and MUSE did the same for hot ionized gas."
The ALMA and MUSE data were combined with a new ultra-deep observation of NASA's Chandra X-ray Observatory cluster, which revealed the hot phase of this fountain in exquisite detail, the researchers observed.
The observations also very convincingly support the hypothesis that the hot ionized and cold molecular nebulae are one, with the hot ionized gas that is simply the "shell" around the cold molecular nuclei that agitate the 39, interior of this fountain of galaxies.
This multiwavelength approach offers an uncommon picture of this system. "It's like looking at the rain cloud, the rain and the puddles at the same time," Tremblay observed. While this is only an observation of a galaxy, astronomers speculate that they are observing a process that is common in galaxies and fundamental to their evolution.
Image: Clouds hover around our local supermassive black hole
G. R. Tremblay et al. A galactic-scale fountain of cold molecular gas pumped from a black hole, The Astrophysical Journal (2018). DOI: 10.3847 / 1538-4357 / aad6dd