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How are dormant supermassive black holes in galaxies connected to past quasar activity?
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Quasar
Six quasar host galaxies, as observed by the Hubble Space Telescope.
Shown are apparently normal, solitary galaxies (left), colliding galaxies (centre), and merging galaxies (right).
Dormant supermassive black holes found in the centers of most massive galaxies are considered the remnants of past quasar activity.1
The connection between these states is defined by a life cycle of episodic accretion:
- Active Phase: Quasar activity occurs when a central supermassive black hole accretes gas at a high rate, a process potentially triggered by galactic mergers. During this phase, the intense radiation, jets, and outflows from the black hole can heat or entirely remove the interstellar medium from the host galaxy.12
- Transition to Dormancy: This expulsion of gas eventually chokes off the fuel supply for the black hole, effectively shutting down both star formation and the quasar phenomenon itself.1
- Dormant State: Once the fuel is exhausted, the black hole becomes dormant. Many galaxies that appear quiet today are believed to have been active quasars in their earlier history, with their current central black holes representing the "frozen" mass accumulated during those past energetic episodes.13