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Winds of black holes shape galaxies

Multi-wavelength observations have offered a more complete picture of high-speed molecular gas expelled from massive black holes. EU-funded scientists analysed the observations to discover how outflows affect star formation throughout the host galaxy.
Winds of black holes shape galaxies
At the centre of every galaxy is a massive black hole. Sagittarius A* at the centre of the Milky Way is quiescent, but at the centre of young galaxies looms the opposite. There are plenty of active galactic nuclei (AGN) in the nearby universe. Astronomers look at merging galaxies to discover how these black holes become active.

With EU funding of the project BLACK HOLES AND JWST (How active black holes shape the universe: Beyond Hubble), astronomers analysed observations of cold molecular gas and dust of the Dragonfly galaxy. Also known as MRC0152-209, this is one of the most rigorously star-forming radio galaxies in the universe.

Observations from the Atacama Large Millimeter Array (ALMA) in Chile and the Australia Telescope Compact Array (ATCA) revealed widespread debris from a merger. Specifically, the Dragonfly galaxy is likely a gas-rich triple merger. But what triggered its star-forming activity?

The BLACK HOLES AND JWST team found that it consists of a close double nucleus and a weak cold molecular gas emitter at a distance of about 10 kiloparsecs (kpc). The powerful AGN seems to have been 'turned on' at this precoalescence stage of the merger.

The cold molecular gas is being displaced within the merger, from which it will probably not escape. Astronomers estimated that the rate at which the molecular gas is redistributed is at least 1 200 solar masses per year and could increase up to 3 000 solar masses per year, which is the star formation limit.

Gravitational interaction between the rotating discs of cold molecular gas around the two nuclei or AGN-driven outflows could drive the gas redistribution. On the other hand, the gas redistribution timescales are similar to those of observed gas depletion, suggesting that these processes are of importance in the evolution of galaxies.

BLACK HOLES AND JWST results mark a crucial step in understanding how galaxy mergers 'turn on' black holes. To all appearances, the destructive force of black holes was found to also create the conditions necessary for the formation of new stars in the outskirts of their host galaxies.

Related information


Black holes, molecular gas, active galactic nuclei, BLACK HOLES AND JWST, Dragonfly galaxy
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