User:InfobyX/Cosmic wind

Lead
Cosmic wind is a powerful force that ejects interstellar gas out, from galaxies, O and B stars, and black holes. These winds push out interstellar materials from galaxy clusters, supernovae and black holes, and redistribute them out into the universe which plays a role in galaxy evolution.

Description
These winds come from the thermal expansion of galactic halos in O and B stars and are further increased by cosmic rays, which shoot out and help push gas out of the halo and disk of its galaxy. In these supernovae, these winds are a result of the conversion of the supernova's thermal energy into kinetic energy which is also further increased by cosmic rays. It is a combination of these hot and cooling flows that cause cosmic wind. In smaller stars, such as the sun, the wind comes from the sun's corona and is referred to as solar wind.

Observations
When viewing the absorption line of an accretion disk of a black hole, if there is cosmic wind then the absorption line will be different. Before 2007, this was only theorized to occur but several physicists including an astrophysicist named Andrew Robinson analyzed the accretion disk of galaxy that is about 3 billion light years away from the Milky Way. They used the William Herschel Telescope to observe this galaxy, and they noticed that the light surrounding the accretion disk was rotating at similar speeds, proving that accretion disks do release winds.

Calculations
A method used to calculate these winds is done by using the absorption lines. At low redshifts of ultraviolet star forming galaxies, the outflow velocity and mass loading factor of the wind, scale with the star formation rate (SFR) and stellar mass of the galaxy. The surface area of these winds can be estimated by finding the radius, in a case of a spherically symmetric wind with a thin shell the formula to find this is $$M_{wind} = 4{\pi}r^2_{wind}f_{cov}N_Hm_H\mu $$, where $$f_{cov}$$ is the covering fraction, $$r_{wind}$$ the radius, $$N_H$$ the column density of Hydrogen atoms, $$m_H$$ the mass of the hydrogen atoms, and $$\mu$$ is the mean molecular weight.