Supermassive black holes may favor the formation of new stars

Active galaxy in the heart of the Phoenix Cluster with its jets (Image ALMA (ESO/NAOJ/NRAO) H.Russell, et al.; NASA/ESA Hubble; NASA/CXC/MIT/M.McDonald et al.; B. Saxton (NRAO/AUI/NSF))
Active galaxy in the heart of the Phoenix Cluster with its jets (Image ALMA (ESO/NAOJ/NRAO) H.Russell, et al.; NASA/ESA Hubble; NASA/CXC/MIT/M.McDonald et al.; B. Saxton (NRAO/AUI/NSF))

An article published in “Astrophysical Journal” describes a research showing a link between a supermassive black hole and the galaxy that hosts it. A team of researchers used the ALMA radio telescope to study a galaxy in the heart of the Phoenix Cluster which has at its core a supermassive black hole that emits electromagnetic radiation jets that are stimulating the birth of new stars.

The Phoenix Cluster, also known as SPT-CL J2344-4243, which is about 5.7 billion light years away from Earth, is one of the most massive galaxy clusters known stretching more than 7 million light years. In its heart there’s a galaxy that has an active galactic nucleus (AGN), meaning a supermassive black hole surrounded by a ring of gas and dust heated by the gravitational energy of the black hole that also emits powerful jets of electromagnetic radiation in opposite directions into intergalactic space.

Previous research carried out using NASA’s Chandra X-ray observatory showed that this active galactic nucleus’ jets are carving a couple of “radio bubbles”, enormous cavities in the middle of the hot plasma that surrounds the galaxy. Those bubbles should create conditions that wouldn’t allow the hot gas to cool down and condense, a condition needed for star formation, instead the new research with the ALMA radio telescope showed a different situation.

The observations with ALMA revealed long filaments of cold molecular gas that is condensing around the radio bubbles’ outer edges. Those filaments extend up to 82,000 light years from both sides of the active galactic nucleus and contain an amount of gas sufficient to form ten billion stars like the Sun. It’s a connection between an active galactic nucleus and the abundance of cold molecular gas hitherto unknown.

It all starts with the supermassive black hole that feeds on gas and dust, the same materials that are used for star formation, so one would assume that its presence interferes with the birth of new stars. However, the electromagnetic radiation jets that warm the galactic core also appear to stimulate the production of cold gases.

It’s a surprising result for the researchers, who see a supermassive black hole that acts as a kind of thermostat that heats up gas and dust around it but on the other hand cools them down in other areas. That black hole has a mass that is already really immense, around twenty billion solar masses, and keeps on growing but the scientists say this will go on for no more than a hundred million years.

The ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope, inaugurated in March 2013, with its power and sensitivity is helping astronomers understand the processes taking place within an active galactic nucleus. In this case, there was a surprising discovery that provides new information on the evolution of active galaxies.

Phoenix Cluster (Image NASA/Chandra Space Telescope)
Phoenix Cluster (Image NASA/Chandra Space Telescope)

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