Outflows and winds from black holes that influence galactic environments and star formation.Black hole winds are powerful outflows of gas driven by the intense radiation and magnetic fields near a black hole. These winds can travel at speeds up to a significant fraction of the speed of light and carry enormous amounts of energy and momentum into the surrounding galaxy. They are not just a byproduct of black hole feeding; they actively shape their host galaxies by compressing gas clouds, triggering or suppressing star formation, and distributing heavy elements across vast distances.
The concept of black hole winds emerged in the 1990s with observations of broad absorption lines in quasars, which indicated high-velocity outflows. The connection to galactic-scale feedback was established in the 2000s through simulations and observations of massive outflows in galaxies with active black holes.
When matter falls toward a black hole, it forms a hot, swirling accretion disk. The intense radiation from this disk can push on the outer layers of gas, accelerating them outward in a wind. Alternatively, magnetic fields twisted by the disk's rotation can launch jets and outflows. These winds interact with the interstellar medium, creating shocks that heat the gas and either compress it to form new stars or blow it away entirely, depending on the density and velocity of the wind. On galactic scales, these outflows can expel gas from the galaxy, starving it of the fuel needed for future star formation.
Understanding black hole winds is essential for modeling galaxy evolution and the growth of supermassive black holes. It also informs interpretations of observations from X-ray and radio telescopes, such as the recent detection of a galactic wind from Sagittarius A*, the black hole at the center of the Milky Way.
Some black hole winds are so powerful that they can blow away the gas from an entire galaxy, effectively turning off star formation for hundreds of millions of years.
| r_{\rm inf} | variable | Influence radius — radius metre |
| M_{\rm BH} | variable | Black hole mass — mass kilogram |
| \sigma | variable | Velocity dispersion of stars — velocity dispersion metre per second |
| G | constant | Newtonian gravitational constant — gravitational constant = 6.67430e-11 cubic metre per kilogram per second squared |








